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THE

ECONOMY OF THE EYES :
PRECEPTS

FOR

THE IMPROVEMENT AND PRESERVATION

OF

THE SIGHT.

FLAIN RULES WHICH WILL ENABLE ALL TO JUDGE
EXACTLY WHEW, AND WHAT

SPECTACLES

ARE BEST CALCULATED FOR THEIR EYES;
OBSERVATIONS

ON

OPERA GLASSES AND THEATRES,

AND AN ACCOUNT OF

STfte Uancrattc Jfltefintft'er,

FOR DOUBLE STARS, AND DAY TELESCOPES.

Qui Visum, Vitam dat."

By WILLIAM KITCHINER, M.D.

Author of The Cook's Oracle ; The Art of Invigorating and Prolonging

Life ; The Pleasure of Making a Will ; Observations on Singing,

&o. &c; and Editor of The Loyal, National,

and Sea Songs of England.

V
BOSTON :

WELLS AND LILLY — COURT-STREET.
1824.

/ '?

: h ■->

CONTENTS.

PAGE

Prefacf, to be read after the Work ... 1

Introduction 2

Spectacles for the poor 9

Chap. I. On Reading Glasses for Persons
whose Eyes are impaired by Age; and
Single Eye Glasses for the Short-sight-
ed .. . 10

II. Spectacles with Plain Glasses . . 16

III. Cases of Persons who could not read

in Spectacles .... 18 and 31

IV. Hand Spectacles . . . . 14 and 19

V. Symptoms of the Eyes requiring Specta-
cles To READ WITH . . . • .21

VI. Of Preservers 27

VII. Table of the Focal Length of the
Magnifying Glasses required at vari-
ous Ages 30

The time that the First Glasses of 36 Inches fo-
cus will assist the Sight sufficiently . . 33
^VIII. When to change the First Specta-
cles 34

The Premature Use of Spectacles, how perni-
cious to the Sight . . . . .29

IX. My Grandmother's Spectacles . . 36
Spectacles for Gourmands . . . .37

X. Hints to Persons choosing Spectacles 40

Divided Spectacle Glasses . . . .44
Plan for Preserving the Sight . . .46

XI. Hints to Persons beginning to wear
Spectacles ; and of Reading -Lamps and

ir CONTENTS.

Candlesticks 52

Case of Dimness of Sight from Over-exercise

of the Eye 59

Of tkt Pole. Star ...... 61

Of the Double Ring of Saturn - . . .62
Contents of the Second Part of the Economy

of the Eyes .65

**-«• Magnifiers for Artists . . . . .67

Concaves for reducing Miniatures . . .70

Nervous Dimness of Sight . . . .71

Ointment for the Eye-lids . . . 72

Chap. XII. Precepts for improving and

Preserving the Si ht . . . .73
The Circumspector ... 75 and 181
Sight-Strengtheners for Painters, &c. . • 7 '

Double Rising Desk 79

1 Reading Candlestick • 81

Green or Coloured Glasses . . . .82
To keep Glasses perfectly clean . . .84

XIII. Glasses for Short-sighted Persons 85
History of the Author's Case of Spectacles . 86
Invisible Opera Glasses . . . . .93
The Disadvantages and the Advantages of be-
ing Short-sighted . . . • .94

XIV. Spectacle Frames . . • .96

Silver Frames 96

Tortoise-shell Do 96

Blued Steel Do. . . -. . . .97
The Length of the Bridge . . . .98
Mean Distance between the Eyes . . .98
Width of a common Spectacle Frame . . 99
How many Tears shed Daily . . . 100

* Proper Shape for the Openings which hold

the Glasses 101

Length of the First Joint . . . .102

Prices of Spectacles . .... 103

XV. Of the aTTALiTYOF Spectacle Glass-
es, AND HOW TO MEASURE THEIR FOCAL

Length ....... 103

XVI. Pebbles . . . , . . • ™ Q

CONTENTS.

perfect

The expense of the Best Glasses is a Groat per

Annum .......

Chap. XVII. On the various Degrees of the
Perfection of the Eye and ear

The Gritty Chord

The Ocular Harpsichord

Beef and Cabbage, the music of

Good Sense and Good Senses

Perfect Senses ....

Bad Senses

Advantages of Insensibility

Pancratic Eye-tube

Portraits of Double Stars

Day Telescopes, how to use with
Vision and with effective Power

et Geminorum seen double . •

c Bobtis do

Hints to Observers of Double Stars .

Hints to Dumpy Fanciers

Newtonian Diagonal Eye-piece

Advice to Buyers of Telescopes
XVIII. Opera Glasses

How to adjust an Opera Glass for various Eyes,
and for various Ages, and Objects at diffe-
rent distances

How to hold an Opera Glass

Field of View in an Opera Glass

The Grand Dandy Opera Glass

The Stops ....

The Opening of the Pupil

Revolving Eye-head

French Operas

English do ...

Magnifying Power, how to vary

To see if any of the Object Glass is cut off

Diameter of Eye-glass
Do. Eye-head

Average Distance the common Eye can

109

109
110
110
112
113
115
116
117
118
121

124
125
125
126
123
133
143
146

148
148
152
152
153
156
157
157
158
158
159
160
161

distinctly the Expression of the Countenance 16.1

Yl CONTENTS.

Average Distance between Spectators and Per-

formers , 2g2

Requisite Magnifying Power to enable a Person
to see as distinctly as if they were within 15
feet of the Stage . , , . . . 162
The Bell Opera with one sliding Tube the best 162
Of Operas which have many Tubes . . 162
Operas for the extremely Short-sighted . . 164
Operas that have no focus „ 164

Invisible Opera Glasses ... 93 and 165
Opera for a Picture Gallery .... 166
Opera for sweeping for a Comet . . . 166

The Ouranologia 166

Binocular Opera 167

Single Object Glasses ..... 168

Concave Eye-glasses for varying the Magnify-
ing Power ....... 169

To ascertain the relative Powers of Eye-
Glasses . . . ... • • 169

Imperfections in Opera Glasses, to discover „ 171
Prices of Opera Glasses , 171

Cautions in trying Opera Glasses . . . 172
Comparisons of Single and Double Object
Glasses ....... 174

To measure the Magnifying Powers . . 178

Diagonal Opera Glass ..... 181

Circumspector .... 75 and 181

Chap. XIX. Theatres ...... 183

Distance from the Curtain to the Boxes at the
English Opera House ..... 184

Ditto at Drury Lane . 184

Ditto at Covent Garden ..... 184

Of the Extension of the Voice . , .186

Mr. Arnold's Theatre 188

Mr. Garrick's ....... 188

Account of the Expense of Building the present
Drury Lane Theatre .... 189—191

Number of Seats, &c. in the English Opera

House 190

Ditto, Druvv Lane f , . . . . 192

CONTENTS. Vll

Number of Seats, &c. in Covent Garden . 192

Ditto, Hayraarket 192

God ! save the King 193

Ditto, the Words marked as they ought to be
sung 193

APPENDIX,

RESPECTING SPECTACLES.

No. I. Rules for Choosing Spectacles, by George

Adams, Optician 201

II. George Adams on Short-sightedness . 203

III. Of Optometers 204

IV. Dr. Smith's Rules for Choosing Spectacles 205
V. Indistinctness in Old Eyes how caused and

how cured, by Dr. Jurin .... 207
VI. Curious Experiment ..... 209

VII. Dr. Wells on the changes which the Vision

of Short-siehted Persons undergoes from
Age . 211

VIII. Mr. Ware's Observations on the Near and

Distant Sight of different Persons . .214
IX. Appendix to Mr. Ware's Paper, by Sir

Charles Blagdebt .... 21S

X. Sir William Herschel on the Apertures

of the Pupil of the Eye . . . .221
XI. Snow Spectacles ...... 224

Viii DESCRIPTION OF PLATES, &C

Eocplanation of the Plate fronting the Title*

Fig. I. Is the Spectacle front recommended for Eyes
in general ; the distance between the centres of the open-
ings which held the Glasses being 2 1-2 inches, i. e. the
average distance between the centres of the Eyes.

Fig. II. Is a portrait of the Pupil of the Eye when in
a state of expansion. See Chapter XII. page 73, and No,
X. of the Appendix.

Fig. III. The Pupil in its most contracted state. See
page 73, &c.

Fig. IV. Convenient double Folding Hand Spectacles.
See page 20.

Fig. V. A Preserver, or the First Sight for Long
Sighted Eyes, i. e. a Convex lens of 36 inches focus cut in
half — to shew its form, &c. the thickness of it at the middle
and at the margin of it. See page 27.

Fig. VI. The 8th Sight, for Long Sighted Eyes— or
12 Inches focus.

Fig. VII. No. 1 Concave, or the First Sight for Short
Sighted Persons. See Chapter XIII. page 85.

Fig. VIII. No. 12 Concave, or the 12th Sight for
Short Sighted Persons.

The Plate of the Pancratic Eye-Tube and Double
Stars to face page 118.

PREFACE.

TO BE READ AFTER THE WORK.

N ow, friendly Reader, before I take leave
of You— after — Your deliberate perusal of
this Volume, — if You vote that my labour has
been lost, or has afforded you so little plea-
sure, that You begin to think You would ra-
ther have your Seven Shillings in your pock-
et again, than this first part of " the Economy
of the Eyes" under your Chin, — allow me to
suggest, that You ought to Lend it to every
body You know — to prevent others being de-
coyed, as in such case You will suppose you
have been — to buy a Book which is not worth
reading.

But if it so happen that fortunately for the
Writer, You think you have derived Amuse-
ment or Instruction from his Work,— -if You
are so good as to wish to be grateful for the
Information which it has given you — Lend it
not — to one of those prudent folks who are
in the habit of borrowing your New Books,
and so contrive to become wise at your ex-
pense, — but do the Author the favour to re-
commend all your Friends to purchase it*
1

INTRODUCTION,

GENERAL OBSERVATIONS ON SPECTACLES.

Without Spectacles* all the other working
tools, of most Artists, soon after their 40th
year, would be almost useless.

At that precious period of Life, when Ge-
nius begins to wait upon Judgment,! the per-
severing Student would no longer be able to
enjoy the fruits of the labours of his Prede-
cessors, or to preserve the produce of his own
for the benefit of Posterity.

The accomplished Artist, almost as soon as
he acquires his Art, would be incapable of
pursuing it, — the seeds of perfection which
he has been industriously cultivating during

* " Were there no other use of Optics, than the inven-
tion of Spectacles for the help of defective Eyes, I should
think the advantage which mankind receives thereby, in-
ferior to no other benefit whatever, not absolutely requi-
site to support Life." — MoLKfEUx's Optics.

t " The exact time when years have ripened the Judg-
ment, without diminishing the Imagination, by good critics
'is held to be punctually at Forty"— See Martin Scrib-
lerus on the Dunciad, p. 55.

INTRODUCTION. o

the First period of Life, would very soon af-
ter cease to be productive, and, but for the
Eye-invigorating Art of the Optician, his lat-
ter days would be melancholy and forlorn.

It is hoped that hy a little attention to the
following pages, that All who can hear,* may
be enabled to procure precisely such Glasses
as are most proper for them.

Every body is in want of such Information,
because Nobody has given it, — therefore, I
have endeavoured to render it as easily at-
tainable, as it is universally desirable, by
communicating it in such plain terms that
Every body may understand.

The choice of Spectacles is one of those acts
which cannot be properly performed by
proxy — the Sight cannot be perfectly suited,
unless

" Every Eye negociate for itself."

This is so absolutely true, that not only
One Person cannot choose for Another — but
One Eye has often very little notion what
Glass will be best even for its own Brother,
so extremely does the Left Eye occasionally
differ from the Right.

No faculty of man varies more in its na-

* It is presumed, that the majority of the purchasers of
this Work, cannot See ! till they have learned how by the
instructions herein given.

4 INTRODUCTION.

ture, or is susceptible of so high a degree of
Improvement and Refinement by Art, as the
Sense of Sight. The highest degrees of its
discriminating power are acquired slowly
and imperceptibly.

From organic imperfection and neglect of
cultivation,* many People pass through Life
who (it may be said, comparatively,) never
See — i, e. whose Eyes never have the facul-
ty of accurately appreciating either Form —
or Colour : — to very few indeed is it given to
perfectly perceive and portray both.

There cannot be a more evident p^oof of
the general defect in people's Sight — than
the general acceptance of capricious and un-
reasonable Fashions, which appear to be pre-
valent, in proportion that they are in direct
opposition to all the principles of good taste,
and which to a fine Eye, are frequently
frightful, and absolutely painful to behold.

From the different modes of colouring of
different Artists, I suppose that the Eyes of
no two Painters feel exactly the same im-
pression of colours, — and objects, appear of.

* " Every person acquainted with Optics and the nature
of vision, knows that what is generally comprehended un-
der the term Seeing, is a complex operation ; an art ac-
quired by degrees, in which judgment and imagination are
concerned together with simple perception."— CRISP em
Vision, 8vo. 1796, p. 106.

INTRODUCTION. 5

different Colours accordingly as they are
illuminated with different Lights.

*.* The Mole's dim curtain, and the Lynx's beam,"*

Pope.

do not differ more extremely than does the
Sight of different persons — and of the same
persons at different Ages.

The peculiar conformation of the Eyes,
differs quite as much in different persons, as
the construction of their Noses ; — it is just as
impossible to guess exactly what Spectacles
will best suit the Sight of another Person, as
it is to tell what Tunes are most delightful to
his Ear^ — or what Tastes are most delicious
to his Tongue.

Nothing can be more erroneous than the
common notion, that there is an invariable
Rule, that a certain form of Glass is calculated
for a certain Age. No Rule has more excep-
tions :— but this Vulgar Error has been pro-
ductive of great and irremediable Injury to
the Eyes of Thousands !

Hence, the grand desideratum, is to instruct
people how to choose wisely for Themselves
— which, I hope, even those who are totally
unacquainted with the subject may do with
the most perfect ease and accuracy, by the
help of this Treatise, which is not published
for the purpose of recommending some par-
1 *

b INTRODUCTION.

ticular Oculist— or of persuading the reader
that the simplest of all Optical instruments,
spherical Spectacle Glasses, can only be pur-
chased of One Optician :— is not a collection
of crude conceits, — but is a plain impartial
statement of all the Facts I have accumulated
during my consideration of the subject for
30 years past — in which I have

u Nought extenuated, nor set down aught in malice."

My Motto, friendly Reader, is

" Truth, tempered by Good Httmour."

"Men must be taught as if you taught them not,
And things unknown propos'd as things forgot.
Without Good-Breeding, Truth is disapprov'd;
That only, makes superior sense belov'd."

Essay on Criticism,

I do not think it is my Business — I am sure
it is not my Pleasure, to register the various
pretended improvements in Spectacles which
have from time to time been proposed to the
Public, — [Such as the Sympathetic Pebbles —
which "as the Sight alters, they will alter
also to the Sight, by which one pair will last
the wearer for Life," &c. &c. &c. ! ! ! This
would be irksome to the Writer, and useless-
to the Reader. — I shall only mention the most
remarkable.

In 1758, Mr. B, Martin published a pam-
phlet recommending what he called
"VISUAL GLASSES,"

INTRODUCTION. <

the use of which, he assures us, would be
" productive of peculiar advantages," — they
might be — but, by Mr. Adam's account, not
Xo the gentlefolk who bought them.

u The desire men have to increase their
Business, and extend their Fame, has, in many
instances, been the origin of alterations and
inventions, — injurious to Science and detri-
mental to the Public.

" To this we may, with propriety, impute
the invention of Visual Spectacles. But the
good sense of the world, which always, in the
long run, justly appreciates the value of every
invention, now leaves Visual Spectacles to
the neglect they merit." — G. Adam's Essay on
Vision, 8vo. 1792, p. 113.

I beg to be excused saying more, than that
I do not think that any of the Spectacle Glas-
ses which have come before my Eye, have
any superiority over the Common Spherical
Lenses now in general use.

In instituting Experiments for ascertaining
the distinctness and brightness of Spectacle
Glasses — be extremely careful, that the Glass
is not only of exactly the same quality, but
also of exactly the same Focal length — or
any attempt at comparison will be useless.

If one of the Glasses be only of a very lit-
tle shorter focus than the other— objects will

3 INTRODUCTION.

always make a very different, and sometimes
a much stronger impression on the Eye.

To measure the Focal Length of Spectacle
Glasses, see Chapter xv.

To give my Readers all the satisfaction in
my power, — T have added an Appendix—
which contains sufficient corroboration of
what I have asserted on certain important
points, — because — by the time Persons want
Spectacles, tfyey have generally become wise
" in their own conceit," — and have picked up
a parcel of silly prejudices concerning them,
which unless completely -counteracted, and
rectified by the invariable standard of irresis-
tible Truth, — will prevent their deriving that
benefit from this publication, which the Au-
thor heartily wishes that they should receive
to the utmost extent.

I have given Rules for the choice of
Glasses as relates to their degrees of Magni-
fying, — and have also poimed out those cri-
terions by which Ail may judge if the Glasses
are good — and of the right focus — and readi-
ly discover those imperfections in them which
are so common, and so injurious to the Eyes.*

To effectually eradicate erroneous opinions,
and to establish the Truth beyond all doubt.

* See Chapter xvii. " Of the quality of Spectacle
Glasses," and the Note at the foot of page 36.

INTRODUCTION. 9

I know is no easy task — therefore, I have
given an Appendix of Quotations from the
best Authors on the subject — the correctness
of whose Judgment has been established by
Experiment, and has been pronounced indu-
bitable, by universal acceptance — i. e. from
the Writings of Dr. Smith ; — Dr. Jurin ; —
Dr. Porterfield ;— Dr. Blagden ;— Dr. Wells ;
— Dr. Herschell ; — Mr. G. Adams, the Opti-
cian ; — the late Mr. Ware, the Oculist ; — and
Mr. Stevenson, the Oculist; — and for many
valuable facts, I am indebted to that expe-
rienced Optician, Mr. Samuel Pierce, who
was upwards of Thirty Years with Mr. Jesse
Ramsden.

" Palmam qui meruit, ferat."

There could not be a more useful Charity —
than that of providing proper

SPECTACLES FOR THE POOR.

The Best Glasses, set in Single-Jointed Steel
Frames, may be purchased wholesale at the
rate of 18s. per dozen Pairs; — if a Single-
jointed frame is fastened round the head
with a Riband, it may be kept on, almost as
steadily and comfortably as a Double-Jointed
Frame.

For the small sum of 18 Pence the Bene-
volent may enjoy the gratifying reflection of
giving an industrious Workman the power of

iO ON READING GLASSES.

long continuing his labour with undiminished
Ability, and of earning a subsistence till ex-
treme Old Age,

In no way — can so much Good be done with
so little Money !

" Qui Visum, Vitam dat."

The greatest part of the Disorders of the
Eyes of Poor People who are upwards of 45
years of Age, are occasioned by their strain-
ing their Sight for want of Spectacles, — or
by looking through Bad Glasses, — or those
of a Focus not suitable to their Eyes : — I
hope when this is considered by the Over-
seers of the Poor, — The District Societies
for Bettering the Condition of the Poor,
and the Patrons of The Eye Infirmaries,
that they will make the distribution of Spec-
tacles a part of their Bounty.

CHAPTER I.

ON READING GLASSES,

For Persons whose Eyes are impaired by Age —
and Single Eye-Glasses for the Short-Sighted.

When would-be-thought-young Persons,
first feel the necessity of giving their Eyes

ON READING GLASSES. 11

Optical assistance, they are, nevertheless shy
of" mounting Spectacles, which they seem to
consider an inconvenient manner of adver-
tising their Age upon their Nose — not reflect-
ing that they are worn by many persons who
have not seen half their years, but who being
Short Sighted, are obliged to walk about in
Spectacles, or forego the sight of " the Human
Face Divine."

However, they suppose that Spectacles are
such unequivocal evidence of Age and Infir-
mity — that they desire to dispense with exhi-
biting them as long as possible — therefore,
they purchase " a Reading Glass," and ha-
bitually put it up to One and the same Eye,
leaving the other involuntarily to wander ;
— after a few years, the sight of the Idle Eye
becomes of a different focus to that which
has been employed with the Glass — and is
often irreparably impaired.

" These puerile propensities, give rise to a
variety of artifices, by which each individual
endeavours to hide from himself and others,
what no artifice can conceal, and which every
one can discover, in all but himself; — these
endeavours often contribute to hasten the
Evils they are meant to conceal. Opticians
have daily experience of the truth of this
Observation, and in no instance more so than

12 ON READING GLASSES.

in the preference given by many to Reading-
Glasses, (under whatever pretext it may be
covered) merely because they think that the
decay of their Sight, and their advances in
age, are less conspicuous by using a Reading
Glass, than Spectacles : but the Eyes in endea-
vouring to See with a Reading-Glass are con-
siderably strained, and in a short time much
fatigued : and there is another objection to
the use of Reading-Glasses, which arises
from the unsteadiness of the hand, and the
motion of the head, which occasion a perpe-
tual motion of the Glasses, for the Eye en-
deavours to conform itself to each change,
and this tender organ is thereby kept in con-
tinual agitation : to these evils we may add
the dazzling glare and irregular reflexion
from the surface of the Glass, which so weak-
ens the Eyes, that those who accustom them-
selves to a Reading-Glass, are in a short time
obliged to take to Spectacles, and to use them
much older than they otherwise would have
done." — Mr. George Adams on Vision, 8vo.
1739, p. 115.

When persons who have long patronized
One Eye, and slighted the Other, take to
Spectacles, they will (generally) require
Glasses of a different focus for each Eye.

When You go to an Optician's to choose

ON READING GLASSES. 13

Spectacles, the first thing to attend to, is to
look at a Book with each eye alternately, —
and carefully ascertain, if You see equally
well, with both Eyes, with the same Glass,
at exactly the same distance.

Inequality of the Focus of the Eyes, is much
more common than is generally supposed, as
Watchmakers, Engravers, and most Artists
who work with a Magnifier, will tell you ;
they generally work with One and the same &,
Eye— with which, they can see much better
than with the other.

After a certain Age, the relative sharpness
of the sight of the Eyes, varies as much as
does the quickness of the Ears — the Senses
of Hearing,— and of Seeing, begin to fail about
the same time ; — there are few people past
40 who cannot hear better with One Ear, p|
than they can with the Other.

The Eye least used, soon becomes weak,
and in the course of a little time almost use-
less. — This fact, is so little known, that I
have frequently heard persons who up to the
age of 40 have worked their Right Eye—-
and finding it begin to fail, say, they must
begin to teach their left Eye to See — how-
ever, as I told them, they found on trial, that ,
the Eye which had been Idle, was much

14 ON READING GLASSES.

more impaired than that which had been
active.

"By ceaseless action all that is, subsists." Cowper.

Spectacles are always preferable, because
both Eyes* by being kept in action, are kept
in Health — Vision is brighter and easier.
and the labour of each Eye is considerably
lessened.

As the Eyes of Persons who have either a
very Long or a very Short sight, are useless
without Optical assistance — they should have
Double Folding Spectacles slung round
their neck; (See Chapter IV. and Figure
IV. in the Plate fronting the Title ;) or, if
they will have a Single Eye-Glass- — let them
take care to use it without partiality — and
put it to Each Eye alternately.

* To ascertain whether an Object seen with Both Eyes.
appears brighter or larger, than when seen with One Eye
only, Dr. Jurin made several experiments, which are too
long to insert more than the results of them.

" This difference was most conspicuous, .when in making
the experiment by candle-light, the book was at such at
distance from the candles as that there was scarce light
enough to read with both eyes ; when the column which*
was seen by One Eye only, was not at all legible ; but I
could read witb both ; though with some difficulty — See
Dr. Smith's Optics, 4to. vol. ii. p. .107 of Remarks.

" Though the Letters of a printed book appeared brighter
and stronger — yet they do not seem at all larger wheiw
viewed with B >th Eyes than when seen with Qr>e Only"
—See Dr. Prxestjjey on Vision, 4to. 1772, p. 669.'

ON READING GLASSES. 15

A Single Glass, set in a smart Ring, is often
used by Trinket-fanciers merely for Fashion's
sake, by folks who have not the least defect
in their Sight, — and are not aware of the
mischievous consequences of such irritation :
— this pernicious plaything will most assu-
redly, in a very few Years, bring on an f
imperfect vision in One or Both Eyes.

Notwithstanding all the experience col-
lected during the preceding 42 Years — the
Third act of Life, i. e, from 42 to 63-— is as
seldom performed properly, as either of the
former. " The Art of Growing Old with a
Good Grace"--] believe, is onp of those, which
the Ancients termed " Occult Arts" — and it
appears to be almost as little understood, as
that of communicating to our speedily pe-
rishing Body, the unchangeable nature of the
incombustible Asbestos.

Query. Which appears most ridiculous ?
A ¥oimg Man pretending to the Sagacity
and Experience of Age — or an Old Man
affecting the Strength, and Apeing the Alert- . :
ness of Youth ?

The only way that Persons can indulge
their humour of appearing Purblind with
impunity, is to use—

■

16 SPECTACLES WITH PLAIN GLASSES.

CHAPTER II.

SPECTACLES WITH PLAIN GLASSES.

These should be kept by all Opticians,—
who are not seldom puzzled and plagued by
more nice than wise folks, who without any
need of Spectacles, yet hearing their ac-
quaintance talk of how charmingly they can
see in Glasses, they long, like " the Italian
Count,* to be better than well" — and will
not believe, that although they have not the
least occasion for Optical assistance, yet,
without trying all sorts of Glasses, cannot be
convinced, that however this branch of Op-
tics may alleviate the infirmity of the Eyes,
as a Hearing Trumpet does that of the Ear,
yet that when the Eyes are in a healthful
state, they can receive no more assistance
from Glasses, for the ordinary purposes of
the Sight — than a person who is not Deaf
can from a Hearing Trumpet — which, al-
though so serviceable to a person who is
deaf, is not of the least use to one who is no't
deaf.

* Whose Epitaph is — " I was well — wished to be bet-
ter—Took Physic— and Died."

SPECTACLES WITH PLAIN GLASSES. 1 i

« Why has not man a Microscopic Eye ?
For this plain reason, Man is not a Fly.
Say what the use, were finer Optics given
T' inspect a Mite, not comprehend the Heaven !
God, in the nature of each being, founds
Its proper bliss, and sets its proper bounds."

Pope.

That ingenious Optician, the late Mr,
Jesse Ramsden, informed me, that he had
ofttimes more trouble to make obstinate and
ignorant persons understand that the Art of
Optics could not be of any service to them,
than he had to find Glasses for correcting the
most eccentric aberrations from good Vision
— and that he found the only plan of com-
pletely convincing such troublesome Cus-
tomers was, after he thought that they had
sufficiently amused themselves with trying a
variety of Glasses, — and had tired him, — to
give them a pair of Spectacles glassed with
plain Glass — when they would cry out with
rapture — "Aye, these will do, I can see
charmingly in these — why — why didn't You
give me these at first ? ! ! !"

Nothing, short of such ocular demonstra-
tion, could satisfy them.

2*

18 CASE OF A PERSON, &C.

CHAPTER III.

CASE OF A PERSON WHO COULD NOT READ IN

SPECTACLES.

Mr. R. told me that he was once strange-
ly puzzled, by a clever Old Gentlewoman of
79 years of age, for whom he was requested
to make a pair of Spectacles. — She had ap-
plied in vain, to several eminent Opticians,
and no Glass could be found that improved
her Sight.

With all that Ambition to overcome diffi-
culties, which was the ruling passion of
Jesse Ramsden, he waited upon the Lady,
with several pairs of Convex, and of Con-
cave Spectacles, making quite sure, that
however others had failed, he should suc-
ceed, and enjoy one of those triumphs, which
constituted the Zest of his Existence, — but
after patiently trying every one of them, She
said with a Sigh! — "No, — not one of these
will do — I can see better with my Naked
Eye. Well ! what an unfortunate Creature
I am, at my Age, not to be able to see to
read in Spectacles ! !"

Jesse consoled the Good Lady as well as
he could, by observing, that many at her
advanced age could hardly see at all ; and

HAND SPECTACLES. 19

that although she could not see to read

Here she interrupted him with sufficient ve-
hemence, and, to his extreme astonishment,
exclaimed, — " Sir, You are strangely mis-
taken, Sir !— I did not tell you that I could
not see to Read, Sir ! — I can see to Read,
Sir, as well as ever I could, — I only com-
plained that I could not see to read in Spec-
tacles ! ! / can see to read very well without ! ! !
but my Acquaintance say how charmingly
they can see with Glasses, and surely, it is
very hard that I cannot enjoy the same
Advantage."

CHAPTER IV.

HAND SPECTACLES

Are infinitely better than any Reading
Glass,* however large it may be, — but are

* " The Single Convex Glasses with which some Persons
read, must be very injurious, if they be sufficiently large to
admit the same object to be seen with both Eyes. For as
both axes will then pass through them, one on each side of
the centre, the interval of the pupils will be widened, and
the refracting power of the Eyes be diminished; so that
here a disadvantage is to be added to the prejudice of the
convexity of the Glass, — not a benefit to be placed against
it, as in the case of Common Spectacles for the Long-
sighted."— Dr. W. C. Wells on Vision, 8vo. 1792. p. 130.

20 HAND SPECTACLES.

still, not so comfortable to the Sight as Spec-
tacles on Nose — unless considerable care is
constantly taken to always hold them exact-
ly parallel with, and at exactly the same
distance from the Eyes.

Double Folding Hand Spectacles (see Figure
IV. in Plate facing the Title) are preferable
to a Single Eye-Glass, for Short-sighted per-
sons to view pictures, &c. &x. Moreover,
the use of them is not so likely to be set
down to Impertinence and Affectation — a
censure which all persons expose themselves
to, as often as they stare about them with
"« Quizzing Glass."

The ingenuity of the Optician is often dis-
played in the formation of Hand Spectacles,
and a variety of highly-finished Gold and
silver mountings have been contrived — but
unless the Glasses are defended by a case, as
in the frame portrayed in Figure No. IV. in
the Print facing the Title, they will soon
become scratched and spoiled. The Pearl
frame is the most elegant.

SYMPTOMS OF THE EYES, &C. 21

CHAPTER Y.

SYMPTOMS OF THE EYES REQUIRING SPECTA-
CLES TO READ WITH.

The natural decay of the Sight commen-
ces, in Common Eyes, very soon after " the
Meridian of Life," which, according to those
who train men for Athletic Exercises, and
according to Dr. Jameson,* is about our
28th, — according to others,! about our 36th
Year.

" The Crystalline Humour is clear and
transparent like water — till about the 25th
or 30th year of our age, when it begins to
become a little Yellow towards the centre,
which Yellowness grows gradually deeper
and deeper, and extends more and more
towards the surface, in so much that Dr.
Petit found that the Crystalline of a man
81 years old, resembled two pieces of beau-
tiful Yellow Amber." — Dr. Porterfield
on the Eye, 1759, 8vo. vol. i. p. 229.

The commencement and progress of the dete-

* See Dr. J. on the Changes of the Human Body, 8vo.
1811, p. 89. ►.■■■■

t See 4th Edition of " The Art of Invigorating and,
Prolonging Life" by the Author of this Work, 12mo.
1822, p. 46,

22 SYMPTOMS OF THE EYES REQUIRING

rioration of the Sight, depends upon the
health of the individual — upon the original
formation of the Eye, — and upon how it has
been used.

Some Eyes, at 30 years of Age, require
the aid of art as much as others do at 50, —
while the Sight of some persons continues
almost as perfect at 50 as it was at 30.

The average period of the Eyes requiring Spec-
tacles to read with, is about the 45th year.

Nature has decreed, that soon after our
40th year, the most perfect Eyes shall no
longer retain the privilege she gives to Youth,
of the power of adjusting them to See dis-
tinctly at different distances : — this range of
accommodation diminishes gradually, till it
fails almost entirely — those to whom it is
given to continue to discern distant things
.distinctly, — no longer see those which are
near distinctly.

Very few persons past the age of 40 can
see quite so well by Candle-light, as they
could before that Age — those who can, —
will generally nnd that there is a small de-
gree of Shortness in their sight, which is the
cause of their possessing that advantage lon-
ger than persons in general do — if they
will try that very shallow Concave which is
called, by Opticians, " JVo. O. Concave" or

SPECTACLES TO READ WITH. To

" Half a Number" — they will find it give a
decided outline to distant objects, which they
never* saw defined sharply before.

However, people who do not use their
Eyes tor minutely examining Near, — or for
accurately delineating Distant objects. — are
quite unconscious of the finer perceptions of
a fine and cultivated Eye — and are equally
insensible to the smaller gradations of the
deterioration of their Sight, and happily
suppose that " they have a Good Eye, 1 '
while, as Beatrice says,

" They can see a Church by Day-light."

There are several symptoms, too evident,
even for the Self-love of the vainest and the
weakest to mistake, by which All persons
will easily perceive when they really require
the assistance of Spectacles.

The first Indication of the Eye beginning to
be impaired by Age, is that when You wish to
read a small print, You are obliged to remove
it further from your Eye than You have
been accustomed to do, and desire the aid of
plenty of Light ; and on looking at a near
object, it becomes confused, and appears to
have a kind of mist before it. and the letters
of a Book run one into another or appear dou-
ble, &c. ; and, by Candle-light,* You catch

* " There are many who find the effect of Candle-light

24 SYMPTOMS OF THE EYES REQUIRING

yourself holding a Book, &c. close behind
the Candle — and, that you begin to admire
the ingenuity of the Gentleman who invent-
ed Snuffers.

You will begin to feel the absolute necessity of
using Glasses, when you want to read a small
print by Candle-light, for Twelve months before
you require their assistance by Day-light* — See
Cumumbra Lamp,

If You obstinately strive against Nature,
and barbarously refuse your Ejes that assist-
ance from Art — which will enable You to see
with great ease, but without which, you can-
not see without great difficulty — You will act
as absurdly, as if You refused to eat when
hungry, or to sit down when You are tired —
and will soon strain and weaken your Sight.
which will receive more injury in a few
Months by such forced exertion, than it would
in Years, if assisted by proper Glasses which
render Vision easy.

so different from the purer light of Day, that they are
obliged to use Spectacles by night, though they can do very
well without them in the day. These, when the eye has
become more flat, will find it advisable to have two pair of
spectacles, one to use by day, the other appropriated for
the night : by this means, nearly the same quantity of Light
may be brought to act upon the retina at one time as the
other ; thus the eyes will be less fatigued, and longer main-
tain their natural Vigour." — Mr. G. Apams on Vision,
8vo. 1789. p. 103,

SPECTACLES TO READ WITH. 25

However, some people seem to be about
as unwilling to acknowledge this Truth — as
they are to confess thatthey do not feel quite
so frisky as 45 — as they did at 25.

The common objection which people make
to put on Spectacles, is, that " if They once
begin to wear them, They are afraid they can
never leave them off again :" — this is true
enough ; — but why should they ? if by such
aid, their Sight is relieved and preserved,
and They are enabled to see easily and dis-
tinctly, and when they attempt to read with-
out, their Eyes ache, — their Head aches, —
and every bit of 'em aches.

A man afflicted with incurable Lameness,
who cannot move without Crutches, would
act just as wisely, in refusing to avail himself
of them, — because he can never hope to walk
again without.

" Timely assistance from Glasses will ease
the Eyes, and in some degree check their
tendency to grow flatter — whereas, if they be
not assisted in time^ the flatness will be con-
siderably increased, and the Eyes be weak-
ened by the efforts they are compelled to ex-
ert ; all delay is dangerous, and the longer
those who feel the want of assistance, defer
the use of Spectacles, the more they will in-
3

26 SYMPTOMS OF THE EYES, &C.

crease the failure of the Eye." — Adams on
Vision, 1792, 8vo. p. 109.

" The change in the conformation of the
Eyes, which renders Spectacles useful, seems
to be one of those which Nature has destined
to take place at a panicular period of Life,
and to which there is no gradual approach
through the preceding course of Life. A per-
son for instance at 40,sees an object distinctly,
and at the same distance that he did at 20.
When he draws near to 50, the change I have
spoken of, commonly comes on, and obliges
him in a short time to wear Spectacles. As it
proceeds he is under the necessity of using
others of a higher power. But, instead of
supposing that his Sight is gradually becom-
ing worse, from a natural process, he attri-
butes the increase of the defect in it, to his
too early and frequent use of Glasses. Upon
the whole, I should draw this inference from
what has been said, that — no person whose
Sight begins to grow Long, ought to be in the
least prevented from enjoying, the immediate ad-
vantage which Spectacles will afford him, by the
fear that they will ultimately injure his Eyes" —
Dr. Wells on Vision.

OF PRESERVERS. 27

CHAPTER VI.

OF PRESERVERS.

By the help of Convex Glasses* of 36 or 30
Inches focus, if jour Eyes are in the slate
above mentioned, You will be enabled to
read with the same ease, and at the same dis-
tance, that you did before your Sight was
altered by the inevitable decrees of Old
Time — such Glasses, will make things appear
clear, and distinct as they did before your
Eyes were impaired ; and if judiciously cho-
sen, lessen the labour of the Eyes — and ena-
ble them to do their work with more ease,
and therefore, I suppose, do, in a certain de-
gree, preserve the Sight.

This Title of Preservers, which some sa-
gacious name-giver gave to Spectacles of 36
Inches focus or the F : rst Sight, is an admira-
ble appellation to attract the attention ofpeo-

* Of Convexes, — i. e. Glasses for assisting those Eyes
which are too Long Sighted — or what is commonly called
an Old Sight, are named from their focal length ; the high-
est number, No. 36, magnifies least, and is called the 1st
Sight : See Figure 5 in the Plate facing the Title.

Of Concaves, i. e. Glasses for a Short Sight,— that which
is the least concave, and gives the least assistance to the
Eye, is called No. 1. gee Figure 7 in the Plate fronting
the Title.

28 OF PRESERVERS.

pie — but is equally applicable to all the fol-
lowing gradations of Glasses ; — for the terra
is generally misunderstood, — people seera to
suppose, that Spectacles of 36 Inches focus,
have the magic power of arresting the pro-
gress of that failing of the faculty of Sight,
which is one of the natural and unavoidable
consequences of Age.

When once the Sight begins to fail, it con-
tinues to decay, till in extreme Age, our Eyes,
like our other Senses, — become of almost as
little use to us, as they were in our Infancy.

It is very common for Persons after they
have worn Spectacles of 36 Inches focus for
a Year or two, to complain that they think
that " their Glasses cannot be of the right fo-
cus for their Eyes, for when they do not wear
them, they certainly cannot see so well with-
out them as they did before they used them,
therefore, — they certainly cannot be Pre-
servers.''''

After the process of deterioration has been
proceeding for 12 months — it would be won-
derful if it had not made some perceptible
progress ! — It is as ridiculous, to expect that
it L- in the power of an Optical Instrument to
entrely prevent the Eye undergoing that in-
variably certain, although almost impercepti-
ble change which accompanies the advance

OF PRESERVERS. 29

of Age, as it would be to suppose that Art
can prevent the failing of any of our other
faculties.

I make these remarks, because, I know that
the prepossessing term has induced some ex-
cellent Artists,* who were naturally extreme-
ly anxious about their Eyes — (their Eyes are
their Estate, the mainspring of their Fame
and of their Fortune) — to wear Spectacles
"before they wanted them.

Mem.— The premature use of Spectacles, is
as pernicious to the Sight, as Physic to the
Stomach of a Man in Health, and as absurd,
and as uncomfortable, — as it would be to put
on a Fur pelisse at Midsummer, as a Preser-
ver against your feeling the Cold of Christmas.

* See Chapter xiii. The Art of Seeing, &c.

30

FOCAL LENGTH OP

CHAPTER VII.

TABLE

OftheFoca? Length of the Convex or Magnify-
ing Glasses commonly required at Various

Ages.

Years of Age-

Inches Focus
Convexes.

Remark.

40

45
50

36
30

24

Convex Spectacles are
seldom wanted, except to
read by Candle-light till
45 or 50.

55

20

58

18

60

16

65

14

70

12

75

10

80

9

85

8

90

7

100

6

*

* These three last deep Lenses are very rarely required
except for Couched Eyes. " One focus is seldom sufficient
to enable those who have undergone the operation of
Couching, to see objects at different distances— who gene-
rally require one pair of Spectacles for near,, and another

CONVEX GLASSES, &C. " 31

The above Scale was given to me by an
eminent Optician, as the average results of
upwards of 50 Years' very extensive Experi-
ence :- — and I believe it is as good a General
Rule as can be written ; but, as I have ob-
served in the Introduction to this work — JVo
General Rule has more Exceptions,

44 No regular estimate can ever be esta-
blished as an absolute criterion, either of the

for distant, objects. The foci which are used lie between
6 and l£ inches."— G. Adams on Vision, 8vo. 1792, p. 126.

If you are a Laughing Philosopher, gentle Reader, You
will not be very angry with the Author for inserting the
following Anecdote : —

"In the city of Leyden, in Holland, a young woman
lost her sight from a cataract ; the operation of couching
was successfully performed upon her Eyes, and she reco-
vered the use of them; but it appeared that the Visual Or-
gan (as is usual in such cases) was not completely restor-
ed to its primitive condition. Some very singular and un-
accountable anomalies in her Vision presented themselves,
which not a little puzzled the curious in Physiology and
Optics.

" It was ascertained that her Eye was able to define a
certain class of very minute objects with abundant accu-
racy, such as the Eye of a needle, for example, which she
could thread as well as ever ; but on presenting her with a
Book, it was evident that she could not distinguish a sin-
gle letter, but complained that she could see nothing but a
heap of odd marks.

"These facts, no less strange than true, naturally excit-
ed an intense interest among the Medical Professors and
Students ; every one was anxious to distinguish himself by
affording a satisfactory elucidation of these inexplicable
phenomena.

32 FOCAL LENGTH OF

want of, or for the change of Spectacle
Glasses; because, the failure or the strength
of the Sight, varies so considerably with dif-
ferent people : — several youths under 20
years of Age, have applied to me, who could
not see either to read or write, without very
strong Magnifiers of 6 or 8 inches focus —
while°I have met with other persons who
have arrived at 80, able to read a small
print without any."

" That celebrated Preacher, the Rev. Mr.
Romaine, Rector of St. Ann's Blackfriar's,
who died in the Year 1 795, having attained
the age of 81, could read the small print in

" A hundred theories were framed— every one more inge-
nious than the other. The Professors Von Kracbrajver,
and PtrzzLEDORF, favoured their pupils with most excel-
lent lectures on the subject, with which they were greatly
edified. However, none of the disputants succeeded m
establishing a Theory which met with universal approba-
tion. Many of the vulgar still chose to think that all the
said Theories might be liable to the old objection (howev-
er satisfactory and plausible they might appear,) viz.—
' That they were not True.'

" Matters were in this state, when a mischievous rogue
of an Irish student, who took a singular delight in ridi-
culing every thing learned and philosophical, contrived to
insinuate himself into the confidence cf a younger brother
of the Patient's by a present of an extra portion of Dou-
blegilt Gingerbread, which so entirely won the Youngster'*
heart, that he confessed (though with some difficulty) that
to the best of his belief, his Sister "Sarah had never learn-
ed to Read," but unwilling to acknowledge her ignorance,
had made him and all the Family— promise not to tell. '

CONVEX GLASSES, &C. 33

a pocket Bible, unassisted by Glasses, even
to the last. He never wore Spectacles, nor
wanted any."

" I knew a Gentleman who took the assist-
ance of Glasses at about 40 years of Age ;
these after some time he exchanged for older
ones ; and although he lived to be 84, they
were never afterwards altered, and his sight
continued sound and healthy. Knowing this
circumstance, I had the curiosity to measure
the focus of the Glasses, and found it was 14
inches, which he had been using quite satis-
factorily for upwards of 40 years."

" Another Gentleman, now living, with
whom I am well acquainted, did not take to
the use of Spectacles until he was 55 years
of Age: since that period, his Glasses have
been twice or three times changed ; and al-
though he is now but little short of 87, yet
the Glasses which he generally uses, and
which he can see the best with, are 16 inches
focus."

For these last Remarks I am indebted to Mr.
Samuel Pierce.

The time thai the First Glasses of 36 inches
focus will sufficiently assist the Sight — depends
on the peculiar nature of the Eyes — on the

34 WHEN TO CHANGE FIRST SPECTACLES.

wear they have previously had — on their
subsequent exertions — and on the Constitu-
tion and general Health of the Individual.

Persons of a strong Constitution, who make
more use of their Legs and Arms, than they
do of their Eyes, seldom want Spectacles so
soon,— or want to change them so soon, as
the Studious and those Artists who are much
"employed in fine works, which require not
only the most earnest exertions of the Eyes,
but also the application of a powerful Mag-
nifier.

As a general Rule, the first Spectacles will
last You for reading by Daylight, during
your first apprenticeship to Old Age— i. e.
about 7 Years.

CHAPTER VIII.

WHEN TO CHANGE THE FIRST SPECTACLES,
FOR STRONGER MAGNIFIERS.

When You find a recurrence of the Symp-
toms which first prevailed upon You to wear
Spectacles — and begin to see but little or no
better with the first Glasses, than you then
did with your naked Eye— your Eyes re-
quire The Second Sight of 30 inches focus.—

FOR STRONGER MAGNIFIERS. 35

But, I most earnestly entreat my friend the
Reader, to be content with as little assistance
as will enable him to read a Newspaper com-
fortably by Candle light,* at about the same
distance he did before his Sight was impair-
ed — from 8 to 10 inches, is the mean dis-
tance at which common Eyes, in their mean
state, see most distinctly.

When you find that the First Sight of 36
Inches focus, is hardly sufficient help to read
by Candle-light — to examine any very mi-
nute object — i. e. to make pens, &c, You
may get the Second Sight, of 30 Inches focus.
— But pray — only use them, for purposes Tor
which you find the First Sight is quite insuffi-
cient.

Thcjbllowing Advice of Mr. George
Adams, the Optician, is excellent : —

" Those who are careful in following a re-
gular gradation in the change of their Glasses,
may preserve their Eyes to the latest period
of Old Age, and even then be able to enjoy
the comforts and pleasures which arise from
distinct vision. Do not therefore precipi-
tate these changes, lest you should absorb
too soon the resources of Art, and not be

* See Reading Candlestick or Lamp, in The Table of
Contents,

able to find Spectacles of sufficient power."
G. A. on Vision, 8vo. 1789, p. 108.
Many persons have irreparably injured
1 their Eyes, and indeed have worn out their
t sight prematurely — by beginning with Specta-
cles of too Short focus, i. e. which magnify
too much, or as the common expression is,
are too Old.

Nature soon bends to Custom. Eyes which
have been excessively stimulated by too deep
Magnifiers, seldom or never recover their
elasticity. *

CHAPTER IX.

MY GRANDMOTHERS SPECTACLES.

How often a story like the following, is
told to Opticians* by persons coming to
change, what they call their First Specta-
cles.

* There are very few Opticians but what must have seen

instances of Persons who by habituating their Eyes to

Glasses of too short a focus, i. e. of too great a magnifying

power, have so injured those tender organs as to deprive

| them of future assistance from Glasses.

This not un frequently happens to Bargain-hujvters —
who buy their Spectacles of— Hawkers and Pedlars — Toy-
shops, Dealers in Marine Stores, See.

37

When their Optical friend expresses his
surprise to find them choose very old Glasses
of 12 or 10 inches focus, instead of the Se-
cond Sight of 30 inches focus,

They say, " Why, when I thought that I
began to want Glasses, — I recollected — that
there was a pair of nice New Spectacles in my
Grandmother's old Bureau, — and 1 had often
heard the old Gentlewoman say, when she
was past her 70th year— -that she could still
see to read Charmingly with her New
Spectacles ! — and so I thought, that I could
not do better than use those Glasses whose
sight-restoring power I had been Eye-witness
of. — I naturally thought, that they must sure-
ly be capital Spectacles which enabled so
Old a Person to see so well : and when 1 put
them on, I was not disappointed — for they
made every thing appear very big indeed,
and I could read the smallest print very
nicely indeed— -better than I had been able
to do with my naked Eye for a long time
past."

I must now give you a hint, gentle Reader,
— however improper such mighty Magnifiers
may be for your Visual Organs — preserve
them with all care — the occasional use of
them will greatly contribute to preserve that
Grand Organ your Stomach. No " Grand
4

38

Gourmand" who has any pretensions to pru-
dence, should venture to attend a turtle-
feast* without such Sentinels on his Nose —
they are absolutely as indispensable a part
of the paraphernalia of the Banquet — as a
Plate or a Spoon !

The Eye is a mighty and merciless enemy
to the Stomach- — alas ! as the Proverb says,
" it is bigger than the Belly." Now even
supposing your Eye to be as big again, — f
with these powerful Spectacles, your Eyes
may be filled with delight, and your Stomach
also : for the former, will imagine that while
you have been leisurely sipping a small Soup-
plateful, you have been swallowing an im-
mense Tureenful : — What a beautiful delu-
sion ! at once, equally delightful to your Sto-
mach, your Eye, and your Tongue — equally

* "Nothing is more difficult of digestion, or oftener re-
quires the aid of Peristaltic P ^sunders, than the gluti-
_ nous Calipash, which is considered the " Bonne Bouche"
of this surfeiting Farrago."

The usual allowance at a Turtle-Feast is 6 Pounds
live weight per head : —

<' At the Spanish Dinner, at the City of London Tavern,
in August 1808, — 400 Guests attended, and 2500 pounds of
Turtle were consumed."" — See Bell's Weekly Messenger
for August 7, 1808.

Epicure Quin used to say that it was " not safe to sit
down to a Tu;tle Feast at on." of the City Halls, without
A Baskct-hilUd Knife and Fork."" — From page 251 of the
5th Edition of The Cook's Or\cle, 12mo. 1823.

39

magnifying the pleasure of those two most
troublesome of the Senses — the Sight and
the Taste — which are ever the most irration-
ally importunate in their demands, and the
most difficult to be satisfied !

Whenever your Tongue cries out for more
dainties, than your Stomach has previously
plainly told you is agreeable to it — to settle
all the difference of their demands to their
mutual satisfaction, you have nothing to do,
but to — put on your Spectacles, and you may
set to at Calipash and Calipee with impunity ;
for, they will make "a little lark" look like
"A LARGE FOWL,"
and "a penny roll" as big as
" A QUARTERN LOAF ! ! !"

Some Philosophers have said, that Pain
is only imaginary, — we may as justly believe
the same of Hunger; and if a Gentleman
who eats only an Ounce of Mutton, imagines,
by the aid of the>e magnifiers, that he has
eaten a Pound — his Hunger, ought, to be as
fully satisfied.

Mem. The addition to your Optician's
Bill — will soon be overpaid by the subtrac-
tion from your Butcher's and Baker's.

40 HINTS TO PERSONS CHOOSING

CHAPTER X.

HINTS TO PERSONS CHOOSING SPECTACLES TO
READ WITH.

A part of the paraphernalia of an Opti-
cian's counter, is a Book* of rather a small
print, (about the size of the Note at the foot
of this Page) — which is presented to those
who come to choose Spectacles — and such
Glasses are very properly recommended, as
will enable the person to read it — at the
same distance, and with the same ease, that
he could before his Eyes were impaired, u e.
through which the Letters appear perfectly
distinct, and of their natural size.

The first thing to attend to, is to look at a
Book with each Eye alternately (shutting the
other), and carefully ascertain, if you see
equally well, with both Eyes, with the same
Glass, at exactly the same distance. Per-
sons are quite unconscious of the frequent
inequality in the focus of the two Eyes till
they thus try them separately ; when they •
often find that a Glass which will do very
well for one Eye— is of little or no use to

* The Author will be sadly disappointed if in future this
Work is not the Volume chosen for that purpose.

SPECTACLES TO READ WITH. 41

the other, which to be rendered effective
must have a Glass of a different focus.

With Glasses not Convex enough., or, accord-
ing to the common expression, which are
too Young, You will not see clearly, unless
the Book is placed so far from your Eyes,
that the Letters cannot be seen distinctly.

With Glasses too Convex — or too Old — You
will be obliged to bring the Book nearer to
your Eyes than you did when your Sight
was good— and the Letters will appear larger,
than they really are. Spectacles which
magnify too much, will strain the Eyes even
more than those which do not magnify
enough — and instead of retarding, will acce-
lerate the defect which age brings on.

" When persons apply to an Optician for
Spectacles to read or work with; they
should clearly understand, that the Objects
for which such Spectacles are solely calcu-
lated, are not placed more than 12 or 14
Inches from their Eyev — i. e. whether Read-
ing, Writing, Sewing, &c. for there seems to
be a natural impulse in most persons, that
after a printed Book has been handed them
for trial lo read, they will presently look oft*
— to some object on the other side of the
Room, or across the Street, and say, ' Why
now I can see well enough to Read with
4*

42 HINTS TO PERSONS CHOOSING

these Glasses — but I cannot discern what
that word is over yonder Door ;' and the
Optician has oftentimes no little trouble to
convince them, that such Spectacles are not
intended to show objects at a distance — to
see which, their Sight is as strong as ever;
and in fact, that they can see distant objects
best with their naked Eye."

" A person in business, with whom I was
acquainted, began to want the common Opti-
cal assistance, especially for Writing, when
about 40 years of Age— the Glasses he first
used were of 30 Inches focus, but he soon
found them useful to look at the labels on the
parcels of Muslin arranged on the shelves
around his Shop : after a while, he found it
easy and convenient to keep them on during
the Day, to serve his Customers, or occa-
sionally to look along the Street for a passing
friend. Another pair of deeper focus, was
a repeated necessary consequence, for the
mechanism of his Eyes naturally formed
themselves to the power of the Convex
Glasses, and his Eyes still growing older— ^
and strained by too strong excitement, at last"
would not perform their office distinctly,
unless assisted by Spectacles of 1 1 Inches
focus — so that he became literally half-blind
in the course of about f Years,

SPECTACLES TO READ WITH. 43

w This, is not a very singular,— but a very
common case, — and one of the most frequent
causes of irreparable injury to the Eyes,
and is. one of the first cautions to be given to
those who are choosing Convex Spectacles,

" From not being aware of this, I have
known several Painters and other Artists,
who have, in their natural anxiety to see as
well as possible, irremediably injured their
Sight — so that when they became 60 or 70
years of age, they were obliged lo use Two
half glasses of different foci fixed in the
rings of a Spectacle frame — -the upper half
to help them to observe a distant picture or
sketch, &c. and the lower half to transmit it
to canvass." — Mr. S. Pierce.

With such divided Glasses, it requires con-
siderable attention to raise or depress the
Eyes sufficiently, so as only to look through
one half, — and that the rays from the other
half, may not confuse the Eye and distress
its adjustment — which would be extremely
perplexing and detrimental to the Eyes, to
which it would be as bothering, as it would
be to the Ears to have two Barrel Organs at
the same moment, — One playing " Sally in
our Ally," — and the Other " Ally Croaker."

There have been several other plans for
obtaining tne convenience of Two pairs of

44 HINTS TO PERSONS CHOOSING

Spectacles in One frame — by having the
glasses to turn up on the siae, &c. but all
such contrivances are at the expense of the
Eye — the Magnifying power of Spectacles
has also been made [o vary from 36 to 12
Inches focus, by having two Eye-glasses, of
72 inches focus, one before the other, and
separating them ; but the vision cannot be
so good as with the simple single Eye-glass
— and those who value their Eyes — will use
no other. I think the most convenient plan,
and also the least injurious to the Eyes,
would be to have a pair of Spectacles glassed
with Glasses of the focus required to see the
distant object or sketch, &c. and other Glas-
ses in a frame attached to the Spectacle
frame, and moving on hinges — which, when
brought down before the Glasses fixed in the
Spectacle frame — might make combined the
focus required for painting the Picture, and
which, when it was requisite to refer to the
Object, or Sketch, might be turned up on the
Forehead, quite out of the way.

" The late President of the Royal Acade-
my— Benjamin West. Esq. was in the habit
of using Divided Glasses for many years ; the
upper half was of 30 inches focus, and the
lower of 12. But for some time before his
death, which happened when he was about

SPECTACLES TO READ WITH. 45

90 years of age, he had the upper half of 30
inches focus, and the under half of only 8
inches focus." The Glasses were round and
an inch and a half in diameter.

The above account of Mr. West's Specta-
cles is another of the contributions of Mr. S.
Pierce, who made the Spectacles.

By trying a variety* of Glasses at an Op-
tician's, the Sight soon becomes confused
and tired, and for the moment quite unfit to
appreciate with proper accuracy, what Glas-
ses are exactly the best for it.

I advise persons who have never worn
Spectacles — or are uncertain what Glasses
will suit their Eyes best, to borrow One of
the Sets of Glasses, which consist of Specta-

* Though in the choice of Spectacles, every one must
finally determine for himself, which are the Glasses through
which he obtains the most distinct Vision ; — yet some con-
fidence should be placed in the judgment of the Artist of
whom they are purchased, and some attention paid to his
directions.

" By trying many Spectacles the Eye is fatigued, as the
Pupil varies in size with every different Glass, and the
Eye endeavours to accommodate itself to every change
that is produced. Hence the purchaser often fixes upon a
pair of Spectacles not the best adapted to his Sight, but
those which seem to relieve him most, while his Eyes are
in a forced and unnatural state ; and consequently, when
he gets home, and they are returned to their natural state,
he finds what he had chosen, fatiguing and injurious to the
sight." Mr. G. Adams on Vision, 8vo. 1789, p. 96.

46 HINTS TO PERSONS CHOOSING

cles, of regular gradations of power, set in a
frame — the first set of Convexes usually con-
tains the first Seven Glasses mentioned in the
Table at page 30 — or, if these cannot be had
— c Loose at the Opticians, those Spectacles
which they think they can see best with,
and take home with them also, Two other
pairs, one a degree more, the other a degree
less Convex, or Concave, as they happen to
be either Long, or Short-Sighted : — they
should try these repeatedly for whatever
purpose they wish to employ them : — should
take care, that the Glasses they try are all
perfectly clean — and that they hold them as
close and parallel to the Eye as Spectacles
are placed.

They will probably find, if they try them
by Candlelight, especially with a very small
print or fine work — that one degree of mag-
nifying power more than they require by
Daylight, will show very small objects most
distinctly— hut I protest against such indul-
gence at first — when the Sight is much im-
paired by Age — a pair of Glasses for use by
Day, and another for Night, are advisable
comforts for the Eyes.

The best plan for the Preservation of the Eyes,
— is not to employ them in any work at Night
that gives them any trouble : — let all Bust-

SPECTACLES TO READ WITH. 47

ness which requires intense attention, such as
mending Pens, &c. be done by " the better
Day."

At any Age, — the less the Eyes are ac-
tively employed at Night, the better — after
the labours of the Day, the Eye participates
in that languor which every other part of the
System suffers, and the tone of the Visual
Organ* is comparatively feeble— therefore
avoid as much as possible, reading a small
print, or any business which requires the
earnest exertion of the Eyes — and always
use a shaded light.

The moment that your Eyes, by beginning
to feel hot and fatigued, give you a hint, that
they have done as much work for you as is
agreeable to them — leave off exerting them.

Forcing the Eyes to Work at Night* e^en
for a few moments after they are tired, — will
often, put them out of humour for the whole
of the following Day, and is of all Eye-spoil-
ing Acts the most mischievous ; — want of
Mercy in this respect, has prematurely ruined
the Eyes of Thousands !

Several Young Ladies, of only about 25

* « The frivolous attention of a quarter of an hour of %
an Evening, has cost many, the comfortable and perfect
use of their Eyes for many years : — the mischief is effected
imperceptibly — the consequences are irreparable." — Mr,
G. Adams on Vision, 8vo. 1789, p. 98.

43 HINTS TO PERSONS CHOOSING

years of Age, have complained to me that
they could not work without Spectacles of 30
Inches focus — who I found, on inquiry, very
justly attributed this premature failure of
their Sight to having been obliged frequently
to sit up at Needle-work half the Night dur-
ing the time they were with Dress-makers.

Those who have any regard for the Eyes of
their Children — will make it part of the agree-
ment, when they article them to any Business
requiring the earnest exertion of their Eyes,
that they shall never be required, on any
pretence, to use them at latest after .Nine
o'clock at Night.

A friend of the Author, who has passed his
60th year, and has found it necessary to use
Spectacles ever since he attained the age at
which they are usually wanted ; whose oc-
cupations have occasioned his Eyes to be
constantly employed on small objects in print,
writing, and drawing, by Candlelight as well
as in the Day, by careful management, is still
enabled to see with Spectacles of the first
power, or 36 inche- focal length, for common
purposes ; — i. e. for reading moderately sized
prints, and writing in Day-light.

His practice has been, from the period of

SPECTACLES TO READ WITH. 49

first using Spectacles, never to employ a
higher power than was immediately and ab-
solutely wanted for the particular occasion,
—for which purpose he constantly carries
with him Two pair of Spectacles; one pair
of 36 inches, and another pair of 24 inches
focal length ; the two pair put on together,
serving him for a magnifying power of 12 in-
ches focal length for extraordinary purposes.

The Two pair of Spectacles are for the
convenience of being carried in the pocket :
at Home, in his study, he has by him all the
gradations of 36, 30, 24, 18, and 12 inches
focal length, to be used as required.

He observes, that immediately after using
Spectacles of a high magnifying power, the
Sight does not easily accommodate itself to
a lower power ; and in such cases, it is ne-
cessary to give the Eyes a little time to rest
and recover themselves.

This strain of the Eye, and occasion for
Spectacles of a high magnifying power, is
particularly found in Mending Pens ;* when
the inconvenience of the Eye not readily re-
storing itself to the capability of seeing with
the ordinary Spectacles is strongly evinced :

* Those who find the Mending of Pens rather a difficult
Job ; I recommend the occasional use of a Steel< Pen —
especially when they wish to write verv small and neatly,

5

60 HINTS TO PERSONS CHOOSING

to avoid the distressing inconvenience, he has
a sufficient number of Pens,* to prevent the
necessity of mending any of them until he
has finished writing. — This method of using
the higher powers when the lower powers
will not be soon after wanted, is always a
provident procedure.

There is a convenience in Spectacles of a
small power, while they can be used. No
object can be distinctly seen through Spec-
tacles which magnify very much, beyond
their focal length ; and in using the high
magnifying power of 12 inches focal length,
prints and writings to be referred to must be
placed within that distance of the eye ; but
with the smaller power of 36 inches focal
length such objects may be placed to that
greater distance from the Eye for being re-
ferred to.f

Therefore the smaller the power, provided
it be sufficient, the more pleasant and conve-
nient will be the Spectacles.

* Mending Pens, and all operations requiring the Sight
to be in its best condition, should be attended to early in
the Day while the Nerves are brisk, and before the Eyes
are fatigued : provided the higher magnifying powers are
not wanted for this purpose. \

t This supposes a good light, and the object not very
minute : but such as could be distinguished at the same
distance by the best eyes without glasses.

SPECTACLES TO READ WITH. 51

By placing upright against a wall, a paper
with moderately large printed letters, such
as usually occur in the title-pages of Octavo
books, he finds the greatest distance he can
distinctly see the letters with a good light, to
be the Focal length of the Spectacles. For
the usual method of measuring the Focal
length of Spectacles — See Chapter XV.

If any doubt should be entertained of the
Two Glasses not being of the same focus, he
tries each Glass separately with the same
Eye, and the difference is immediately dis-
covered.

Besides the alteration in the convexity of
the Eye and the muscular power of contrac-
tion and dilatation, Age reduces the vividness
of the illumination on the Retina ; in conse-
quence of which, although objects may be
sufficiently magnified by Spectacles, yet they
tnay be scarcely visible when the light is not
very strong: but. on tho oiher hand, a too
powerful Light is injurious to the Eye. The
Light should th< refore be economized for the
benefit of the Eye. See Chapter XIII.

The Artificial Light from Candles is rare-
ly too strong ; but " the Blaze of Day" is
often too intense on white paper, and should
be moderated by placing the paper so as to
reduce the reflection of the rays of light upon

52 HINTS TO PERSONS

the eye : have enough Light, but no more
than is sufficient.

CHAPTER XI.

HINTS TO PERSONS BEGINNING TO WEAR

SPECTACLES,
AND OF READING LAMPS AND CANDLESTICKS,

When persons first put on Spectacles, if
they have chosen them ever so wisely — still,
they frequently complain that their Eyes feel
fatigued, — and sometimes even ache, after
they have worn them some time, especially
by Candlelight. There is no wonder in this
— t would only be wonderful if they did not.

It usually happens, that for some months
previous to Persons wearing Spectacles, their
Si^ht has either been strained and weakened
by their trying to see what Nature had -de-
creed that they should not, — or, their Eyes
have oeen Idle, and unaccustomed to be used
much, especially by Candlelight.

The cause of the Complaint people so often
make, that their Ejes very soon tire if they
use them at Night, is not, as they seem to
suppose, entirely from the inferiority of Ar-
tificial Light.

BEGINNING TO WEAR SPECTACLES. 53

Mr. Argand's invention gave us all that we
wanted as far as Quantity of Li^ht — and Mr.
Deville informs me that the Gas light from
the Cocoa Nut Oil has the Quality of Day-
light ;'and that with it, the difference of the
colour of Flowers of Sulphur, and that of
Wheat Flour, may be easily distinguished,
which it is difficult, if not impossible, to see
with any other Artificial Light.*

There are some perfectly authenticated in-
stances of persons possessing the faculty of
Sight as to the perception of Form— who had
no sense of Colours — others who could not
distinguish their difference by Candlelight — ■
and one I have met with who by Daylight
cannot tell Red from Green — but recovers
the- power of discerning them correctly by
Candlelight. The latter is a very singular
anomaly of Vision.

* " The greatest part of Objects, in Candlelight, are al-
ways tinged with a Yellow Red, though we are not sensi-
ble thereof; because all the objects in view are changed in
the same proportion. But if in the day-time you place
Candles in a darkened chamber that every thing therein
may be well illuminated, and ' tirt to another place

illuminated with the Sun's light — the Objects illuminated
with Candlelight, when viewed through the door of the
room, will appear tinged with a yellow red, when.compar-
ed with those thai are seen at the same time illustrated
with Daylight. v ' — Dr. PortERFIJELD on the Eye, 8vo.
1759, Vol. I. p. 127.

-5*

54 THE CUMUMBRA LAMP.

THE

CUMUMBRA & SEMIUMBRA LAMPS,

Made at Deville's Manufactory, near Exeter
''Change, Strand.

The shade of this Lamp is' so contrived
that it completely prevents any of its rays
coming to the Eyes — the pupil of which is
therefore regulated solely by the object un-
der examination. Every part of the Frame,
&c. is coloured a dead black.

The faults of all the other Reading Lamps
which J have seen, are, that the shade does
not come either high or low enough to com-
pletely shade the light — and at the top is
partly composed of fretwork which shows the
light through it — and the frames are fre-
quently painted with a light colour, and high-
ly varnished.

To this Lamp may also be fixed a Half
shade, which will screen the Light from the
person reading, and at the same time light
the Room — which in some cases is a very
desirable contrivance.

It is so simple in its construction, that it is
not liable to get out of order, and there is
very little more trouble in trimming it for

THE CUMUMBRA LAMP. 55

Seven hours, — than there is in Once snuffing
a Candle.

It is not only cheap in the purchase, but
in use, for I think it affords more light than
Two Candles at the cost of One. The Oil i
reservoir holds three-fourths of h^lf a pint of /
Oil, which at the present price of the very *y
best Lamp Oil. {5s. 6d. per Gallon,) costs 3
pence, which divided by 12. (the number of
hours it will burn.) gives the expense of this
Light, i. e. A Farthing per Hour. ***-

The Light of the Gumumbra is so good,
that Persons whose Sight is beginning to fail,
and who cannot read by Candlelight with-
out Spectacles of 36 inch focus, with this
Lamp read as w T ell as they can by Day-
light; and so it deserves all the praise which ^^
the pickpocket gave to the Gas light — " It is
as bad as Daylight!" — i. e. for Opticians;
for by the heip of this Lamp persons may
read a year or two longer than they w r ould
be able to do without — and always, with
Glasses of the same magnifying power which
they use by Day.

The effect of a strong Light* I have seen

* " A. person who has been obliged for some years to
use Spectacles in reading, will, in the Sunshine, be able
to read very easily without them." 1 — Dr. PORTERFIELP
on the Eve, 3vo. 1759, Vol. I. p. 162.

56 THE SEMIUMBRA LAMP.

evidenced by the fact — that Persons who
have many years used Spectacles, when the
Sun shines on their Book, can see without.

I believe, that the main Reason why the
Sight is not so sharp at Night as it is in the
Morning, is, that the Eyes are tired, by hav-
ing been at work all Day.

The sensibility of the Si^ht is surprising-
ly recruited by Sleep. Dr. Porterfield, in
p. 38 of Vol. II. of his Essay on the Eye,
observes, "the Pupil is very large upon our
first awaking."

I have for many years been accustomed
to sleep wi f h a light in the Room — and if at
any time it has gone out, I have -generally
awoke just time enough before to previously
light a Candle : and have often wondered,
that the diminution of so faint a light had
such a strong effect on my Eye, as to awaken
me out of a sound Sleep.

1 read the above to Mr. Bundy the Engi-
neer, and he said — " The very same thing
happens to me — I always awake just before
my Night Lamp s^oes quite out."

The best Light for burnirtg 11 night is the
Semiumbra* Chamber Lamp, this may be set
with perfect security on a Table by the
Bedside within reach, and by turning it half

* Made by Devjlle, near Exeter 'Change, Strand.

LAMP LIGHT AND CANDLE LIGHT. 51

round, you may in a moment, have either
Light or Shade — a frame may be made to
carry it over a Bainmarie Saucepan, like the
Nursing Lamps for keeping children's food
warm, which will keep half a pint of Tea or
Broth warm all Night. This will be a great
Comfort to Invalids — especially to those af-
flicted with Nightmare, for which a draught
of hot water will give more immediate, and
more permanent relief, than any remedy I
have tried.

See the Author's own Case in pages 206
to 214 of " The Art of Invigorating Life,"
4th Edit. 12mo. 1822. Published by Hurst
and Co. No. 90, Cheapside.

The strongest objection to Candlelight is,
that the degree of Light given by A Candle,
and its distance from the Eye, is varying
every moment; — A Lamp has not this disad-
vantage : by merely bringing it nearer to, or
removing it farther from the object under
examination, its Light may be either increas-
ed or diminished, and may be adjusted to
almost any degree; and it will continue the
same for several hours.

Those who cannot recollect having played
so much with a new Plaything, " and fancied
toil a Pleasure,'' till the pleasure became a
Toil,— must have a much worse Memory — ■
than I hope you have, gentle Reader !

58 WHEN SPECTACLES ARE WANTED.

I dare say, that " many a time and oft,"
this has happened to all my Readers, — with
much less bewitching Playthings than a pair
of Spectacles must at first be to a person
who after Old Time has for several months
interdicted him from the amusement of
Reading, &c. by this inestimable invention,
finds the full enjoyment of his precious Sight
— suddenly and perfectly restored !

From one of the causes above mentioned,
when persons first put on Spectacles, their
Eyes are generally in a state of weakness, if
not of disease: — moreover, at the Age which
people usually find their Eyes refuse to be
employed on actual service without optical
aid be allowed to them, — (which, as 1 have
before said, happens soon after the 40th
year), the Visual organs occasionally get
out of tune, and participate in that general
deterioration of action which every part of
our Machinery then begins to suffer.

Very soon after we pass the Meridian of
Life, every Sense becomes duller and weak-
er, but no one fails so remarkably, as the
fine faculty of Sight ; — and although Specta-
cles revive the Visual powers;— they cannot
restore to them the untiring energy they
possessed in early life.

Elderly persons can no more play with

WHEN SPECTACLES ARE WANTED. 59

their Eyes, either so well, or so long, as they
did when they were Young— than they can
with their Legs and Arms, &x. ! — to expect
that they can, is about as ridiculous, as to
suppose that Infirmity on Crutches, has any
chance of rivalling the Champion of Pedes-
trians in walking 1000 Miles in 1000 Hours.

Those who consider these things, will
soon cease to be very much surprised, that
their Eyes tire sooner at 60 than they did at
16 — just in proportion, as all their other
faculties become sooner fatigued.

The effective state of the Eyes, like that
of every other part of the Human frame,
depends upon that of the Circulation, — which
depends upon the condition of the Stomach,
and the more or less stimulating Quality,
and the Quantity of the material that it is
supplied with.

Several Studious Persons have told me,
that their Eyes are never in good order
till they have had their Breakfast — that then,
they feel as if they were all Head for three
or four hours — and then, have as irresistible
an' inclination for Bodily Exercise, as the}'
had previously for Intellectual occupation.

Over-exercise* of the Eyes, will occasion

* " The instances of Weakness of Sight which occurred
in the early part of my Ophthalmic practice, were marked,

60 DIMNESS OF SIGHT.

a temporary exhaustion of them, in like man-
. ner as over-exercise of the Legs will disable
a person from walking with his wonted ener-
gy — till Rest restores vigour to him.

I have often heard people complain of
their Eyes being out of humour for several
days, after being exposed 10 the glare of the
lamps at the Theatre, &c. — from being fa-
tigued by sitting up after their accustomed
Hour, — or from other causes which distress-
ed their Nervous System.

When I was 45 years old, I was employed
some hours during several Nights, in look-
ing intently through Reflecting and Achro-
matic Telescopes, endeavouring to ascertain
the comparative Illuminating powers of va-
rious Instruments, — and the effect of various-
ly constructed Magnifiers, for shewing the
Division in the Ring of Saturn, and for sepa-
rating some of the faintest and closest Double
Stars — my Eye became so extremely tired
that the sharpness of my Sight was so sensi-
bly impaired — that for two or three days
after I hardly knew any face that was 20

by great constitutional delicacy, and the individuals had
most clearly brought on the Disease, either by excessive
attention to fine dazzling work, or by inordinate indul-
gence in literary pursuits protracted frequently to late
hours." — Mr. J. Stevenson on Weakness of Sight, 8vo„
1819. p. 57.

THE POLE STAR. 61

feet from me, — and became so much alarm-
ed, that I mentioned it to an eminent Opti-
cian, who said, " Don't be uneasy, the same
thing has happened more than once to my-
self; your Eye has been over-worked — give
it a few days' Rest, and I dare say it will
soon come round again." — His prediction
speedily proved true.

One of the tests to which T put my Eye,
and my 5 feet Achromatic, which has a dou-
ble object glass of 3 T 8 ^ aperture, — was, to
ascertain with how Low, and how High a
power I could see the small Star near the
Pole Star: — it was a decidedly detached
point of light with a single eye-glass, which
gave the Telescope a power of only 28, i. e.
with the 2d E. G. of a compound Astronomi-
cal Eye-piece which magnifies = 44 times —
and it was visible with 20 intermediate Eye-
tubes, the highest of which magnifies 1386
times and is a single Convex lens of the 22d
of an inch focus. — The Object Glass being of
63 Inches focus,
gave, multiplied by 22

126
126

the Magnifying Power J 386
6

62 MAGNIFYING POWERS.

This Instrument is one of the chef-(Vceuvrcs
of the late Mr. Peter Dollond — who thus
speaks of it to the Gentleman he sold it to,
Mr. G. Hodgson, F.R.S., (and of whom I
purchased it,) in his Letter, which is now
before me, dated Nov. 11, 1803:— "It has
been made 10 years, and I can say that it is
one of the best I ever made, and such as I
cannot expect to be able to equal."

This 5 feet Telescope literally deserves to
be called Achromatic, for it shews the disk of
the Moon and of Jupiter as white and as
free from colour as a Reflector ; — to its per-
fect Achromaticism I attribute in great mea-
sure its power of very distinctly shewing the
division in the Ring of Saturn,

The visibility of the dark line, which
proves the Ring to be double, depends not
only upon the distinctness of the image
formed by a Telescope, — but on the power
it has to shew a white object quite white,
and a black one, black.

When Saturn is near the meridian, the di-
vision in its Ring is most plainly visible :
but it may generally be observed Two, an'd
in very fine Nights, Three hours, before it
comes to the Meridian.

Those who wish to see this in London,
are advised that they will not discern the

DOUBLE RING OP SATURN. 63

division in the Ring half so well before — as
after 10 o'Clock.

In this " Elysium of Bricks and Mortar"
we are so surrounded by "Groves of Chim-
neys," that until the majority, of the Great
Fires of the great Manufactories are out —
the obfuscated atmosphere of this monstrous
metropolis defies ail the penetrating power
that the immortal Herschell himself could
bring against it.

Objects which require all the powers of
the Eye to be fresh, and in fine condi-
tion, should not be examined when that Or-
gan is tired with having been at work all
Day.

If a Planet comes to the Meridian at Mid-
night, at 9 or 10 o'Clock lie down in a quiet
darkened room, and rest your Eye by get-
ting a nap previously. A little Horizontal
Refreshment, you will find a proper and
renovating preparative for such Contempla-
tion; — half-an-hour's Siesta will restore the
tone of your Visual Organs, and sharpen
your Sight prodigiously. —

" Experto Crede."

I also saw the small Star near the Polar
Star with my Beauclerc Telescope, which
has a triple Object glass of 46 inches fo«
cus, with a Lens of the 22d of an inch

64 PANCRATIC EYE-TUBE.

focus, which gave this Glass a power of
1012 times.

This singularly perfect Telescope, which
shews Stars as stark neat as ever Nature
permitted them to be seen ; — I purchased at
the sale of Mr. AnberPs Instruments, when
they were sold at his Observatory, at High-
bury Place, by Mr. S. Sotheby, July 24th,
1806: — it was originally fitted up for the
Honourable Topham Beauclerc, and Mr, Rams*
den's name is engraven on the Eye-end of
the Telescope — but Mr. Peter Dollond in-
formed me that he made the Object Glass —
and smiling at the time he gave me this
information, said, " Yes, that Object Glass
is one of the things which is to make me im-
mortal," and 1 then gave him permission to
engrave his title thereto on the tube of the
Telescope.

To have produced such a perfect Instru-
ment is so honourable to the talent of the
artist, that, to avoid all appearance of preju-
dice to either of these eminent men, 1 have
called it by the name of the person it was
made for, Beauclerc.

In the Second Part of " The Economy of
the Eyes," which is now preparing for the
Press,

"Paulo majora canamus" —

PANCRATIC EYE-TUBE, Q5

the Illuminating and Magnifying Powers of
Newtonian, — Gregorian, — Cassegrainian, —
Herschelian Reflectors, — and Galilean, —
Hughenian and Achromatic Refracting Te-
lescopes of various sizes, — will be explained
by Experiments made with 46 Telescopes of
from 3 Inches to 7 Feet focus, which I pur-
chased for that purpose, and have cost me
upwards of £1200 ; and which all who have
Instruments of the like dimensions, may easily
verify at the expense of a few shillings.

A circumstantial account will be given of
their several performances and powers, as
Astronomical and Day Telescopes, — being
the results of 30 years' observation.

To enable my Readers to measure the
respective merits, and the relative reflective
powers of Convex, — Concave — and Plane Small
Specula — I shall lay before them, an abstract
of their several pretensions as stated by pre-
ceding writers thereon ; — then proceed with
those Practical Observations which I have
made myself, and those which I have been
favoured with by several scientific Opticians,
and amongst them those experienced and
excellent Makers of Reflecting Telescopes,
Messrs. Watson — Tuiley — and Cuthbert —
who have given me their Notes and Obser-
vations thereon, and the account of the Facts
6*

66 PANCRATIC EYE-TUBE.

which they have actually ascertained in the
course of their numerous experiments with
Telescopes of various constructions. I have
only room in this page to add, that the Opi-
nions of these eminent Practical Opticians
are perfectly unanimous, and in perfect uni-
son with those published by Sir I. Newton, —
and that I believe, that their Evidence and
Arguments are so true, and so convincing,
and so plainly stated, that they will be per-
fectly satisfactory to the Reader, and will
finally settle certain important points, which
without such Illustration, seem to me, likely
to remain as they are at present —

" Puzzled with Mazes, and perplexed with Errors."

I shall also give an account of the inven-
tion and advantages of the Pancratic Eye-
tube, which to a 3^ Achromatic, gives in the
most perfect manner every degree of Magni-
fying power from 100 to 400 times — which
will be minutely described and explained by
Engravings.

N. B. Contributions on Optical Subjects, ad-
dressed to the Publishers of this Work, wilL
be gratefully acknowledged.
I have mentioned my own case of dimness
of Sight, because, 1 believe many Artists,
from the want of such a hint, have greatly
injured their Eyes, by having been induced

DIMNESS OF SIG^T. 67

by similar Symptoms, prematurely to put on
Spectacles : but, in such cases, " Rest is the
best Remedy."

" So great is the calamity entailed upon
the makers of fine Pieces of Workmanship,
such as Clocks and Watches, that many of
the Workmen are almost Blind before they
arrive at Old Age. 1 know a Jewish Woman
in this City that had a peculiar way of string-
ing of Pearls, so as to cover their blemishes
if there were any, and by that means got a
deal of money; but when she came to be
forty years of age, finding r.o manner of
relief from Spectacles, she was forced to
leave off the Business. 1 remember likewise
to have heard several Printers complain, that
they have given a considerable shock to their
Eye-sight by composing small types.

" In earnest, / do not see how we can afford
any Relief to the Workmen we now treat of ;
for it is not easy to persuade them to leave
a beneficial and lucrative trade ; and Physic
is unprovided zvith any Remedy that can res-tore
the primitive Strength and Mobility of the Eyes,
after the Disorder has become inveterate : for
neither Purging, nor Bleeding, nor other Me-
dicinal Means, can take place in this Case, in
regard the Patients are otherwise Well and
Brisk, and their Spirits being neither clouded

68 MAGNIFIERS FOR ARTISTS.

nor incrassated, it would be improper to
punish an innocent and sound Head with the
Commotions of Medicines.

" However, I would advise such Workmen
/ not only to use Spectacles, but to intermit
from their Work nozo and then, and refresh
their Eyes by Diversity of Objects. For
we can't imagine How much the Mobility of
the Membranes of the Eyes, and the native
Fluidity of the Humours, is kept up by view-
ing divers Objects ; some near at hand, some
remote, some directly, others obliquely ; and,
in fine, all manner of ways i for by this
Means the natural Disposition of the Eye is
preserved, so that the Ball is sometimes con-
tracted, and sometimes dilated ; and the Crys-
talline Humour approaches more or less to
the Pupilla, according as the remoteness or
nearness of the Object requires. Without
this Diversity of Action, the Eyes undergo
the same Fate with the other parts, that, by
being long detained in one position, grow
stiff and unfit for Motion." — Rammazzini mi
the Diseases of Tradesmen, chap. xxix. of the
Eng. Trans. 3vo. 1705, p. 219.

Watch-makers, Engravers, and those who
are in the habit of using Strong Magnifiers,
would feel their Eyes much less fatigued, if
the objects they examine were always placed

MAGNIFIERS TOR ARTISTS. 69

at once, and kept at the proper focus : — this
might be contrived very easily, by fixing the
Magnifying-glass in the opening of a Specta-
cle frame, or on a stand, and making a mark
where the object of examination is most dis-
tinct.

Nothing can be more detrimental to the\
organ of sight than the clumsy practice of -
holding a glass by squeezing the orbicularis
muscle, — this cannot be done without distort-
ing, and distressing, and much injuring the
mechanism of the Eye.

The less the Magnifying Power of the
Glass, the less the Eye will be fatigued by it,
— the less distressing the position of the
Body in working with it, and the larger and
more uniformly distinct the field of view :
and where a moderate Magnifying power is
sufficient — instead of a single Magnifier, I
-think it will be better, especially for Etching,
and for examining the general Effect of En-
graving, &c. to wear Spectacles of 9 inches
focus — with which I think that Artists might
work longer than with only one Eye.

The Compound Magnifiers, which are com-
posed of two plano-convexes with their plane
sides outwards, are very pleasant — as they
have a large and uniformly distinct field.-—
I have not met with any body who was aware

70 CONCAVES FOR ARTISTS.

this construction of Eye-glass was invented
so long ago as appears by the quotation I
here insert : —

" Eustachio Divini hath made a Microscope
with two plano-convex Glasses, which are so
placed as to touch one another in the middle
of their convex surface — and hath this pecu-
liar quality, that it shews the object flat and
not crooked ; and although it takes in much,
yet magnifieth extraordinarily." — See Phil.
Trans, for 1668, Vol. III. p. 842.

Concaves which make objects appear the
size Artists wish to draw them, are very use-
ful to Miniature Painters, who should have
them of two or three different degrees of
Concavity — so mounted on a stem that they
may be used separately or altogether: thus
they may see an object of 6, Feet in diame-
ter reduced to exactly the size it is to be deli-
neated, i. e. to any degree between 6 Inches
in Diameter, and half an inch in Diameter.

The condition of our Corporeal Machinery,
has great influence on that of our Eyes ; —
and indeed of all our Senses. — During that
state of collapse which it is just now the
fashion to call "a Bilious Attack"— or "a
Nervous Paroxysms—just in proportion that
we are out of Heart, — the Circulation is fee-
ble and languid 5 and every sense performs its

DIMNESS OF SIGHT. 71

functions imperfectly. — During such prostra-
tion of the Vital powers, it is not uncommon
to hear people complain of Nervous Deaf-
ness. — It is equally common for them to be
afflicted in an equal degree with Nervous
Dimness of Sight.

This occasional dullness of the Ears, is
oftener observed, than the dimness of the
Eyes ; — because the former defect is obvious
to others, — the latter is confined very much
to ourselves; and unless we happen to want
to minutely examine some minimum visibihj
which requires all the powers of the Sight to
be in full force to be discernible, such a
paroxysm of Ocular obtuseness often passes
unnoticed, and is seldom strong enough to
excite the attention of healthful persons, until
they have passed their 40th year ; who will
then generally find, that it may be traced
either to over-exertion of the Eyes, or to
some Disorder of the Digestive Organs. »

During derangements of the Restorative
Process, for which the Phrase of Fashion
now is when you are Nervous or Bilious —
the Eye-lids are often affected with " Ophthal-
mia Tarsi" i. e. a slight Inflammation and an
increased secretion of the glands about the
Eye-lids— which (in plain English) become
gummed, and when the Eyes are first opened

72 BAD EYES.

in the Morning, the Eye-lids feel stiff and
the Eyes irritable.

The Eye-lids, are much oftener disordered
than The Eyes ; — perhaps three-fourths of
what common people commonly call " Bad
Eyes" are merely disease of The Eye-lids.

I have not space in my little Volume to
descant on One of the 118 Principal Disea-
ses of the Eye enumerated in the Work of
the elaborately minute St. Yves, — but hav-
ing had Ocular demonstration of the efficacy
and innocence of the following Ointment* for
the Eye-lids — I here set it down.

One part of Citrine Ointment,

Three of fresh Lard — mix them thoroughly together
with an Ivory knife.

The Eye-lids are to be anointed with a very

* " Whenever I am informed that the edges of the Eye-
lids have a disposition, be it ever so slight, to adhere to
each other after they have been long in contact, as during
the time of sleep, and when this is accompanied with an
uncomfortable sense of weight in the lids on the approach
of night, in consequence whereof the patient involuntarily
shuts them without being drowsy, and without any particu-
lar stimulus being applied to the Eye to give it pain, I al-
ways suspect that the secretion of the ciliary glands is in
a diseased state ; and in many such cases 1 have found the
success attending the use of the Unguentum Hydrargyri
Nitrati, recommended for the cure of this disorder, quite
as effectual as in those other instances, where the excoria-
tion and redness of the Eye-lids have been visible on the
slightest inspection." — Mr. Ware's Ckirurgical Obs. Vol.
I. p. 116,

PRECEPTS -FOR IMPROVING, &C. 73

little of this Ointment immediately before go-
ing to rest.

The Eye-lids should be washed in luke-
warm water as soon as you rise in the morn-
ing — and every particle adhering to them,
completely, but very gently and carefully re-
moved — which is easiest done by soaking the
Eye-lids by the repealed application of a
soft cloth dipped into warm water till what-
ever sticks to them is loosened. — then you
may proceed cautiously to clean them.

CHAPTER XII.

PRECEPTS FOR IMPROVING AND PRESERVING
THE SIGHT.

The Sensibility of the organ of Sight, is in
proportion to the expansion of the Pupil* of the
Eye, whose mean diameter is commonly cal-

* In the 91st vol. of the Phil. Trans, page 36, in Dr. T.
Young's paper on the Mechanism of the Eye — the Dr. has
given in Plate v. Fig 19, a drawing of the front view of
his left Eye ; " when the Pupil is contracted," the diameter
of it is rather more than a tenth of an inch : and in Fig.
20, " The same view when the Pupil is dilated ;" the latter
measures almost two tenths and a half. See Copies of
these Figures in Plate fronting the Title, Nos. 2 and 3, —
in the openings of the Spectacle frame in the Frontispiece.

?4 PRECEPTS FOR IMPROVING AND

ciliated at about one 10th of an inch-— but
varies in magnitude, from One to at least Two
tenths, according to the brightness of the ob-
ject which is presented to it. — See Dr. Her-
schell's Paper in the Appendix,

When the Light is too strong, or the object
too bright, the Pupil closes in order to inter-
cept that excess of Light* which would oth-
erwise offend the Eye: — when the Light is
faint, the Pupil expands that a greater quan-
tity of it may enter the Eye, and thus make
a stronger impression upon it.

This contraction and dilation of the Pupil,
you may easily discern by holding a looking-
glass before your Eye at a window and turn-
ing gradually round from the window con-
tinually looking at your Eye in the looking-
gl ass _the lowest small speculum of a Gre-
gorian Telescope, as it magnifies a little, will
shew you this still plainer :— and it may be

* " 95. The sensibility of the Eye, and its power to dis-
cern objects without inconvenience by different quantities
of Light is vastly extensive. For instance, the dispropor-
tion in the quantities of Light cast upon the horizon by the
Sun, and Moon, at equal altitudes, I find is no less than
90,000— to 1, when the Moon is full.

"Day-light is to Moon-Ught as the surface of an Hemi-
sphere whose centre is at the Eye, to the part of that sur-
face which appears to be possessed by the enlightened par*
of the Moon : so that the whole Heavens covered with
Moons would only make Day -light."— Dr. Smith's Optics,
4to. 1738, p. 29.

PRESERVING THE SIGHT. 75

easily and perfectly observed by attentively
watching the Eye of another, during such a
change of position : — it is most visible in a
fine full bright blue Eye.

The fact that the sensibility of the Sight*
is in proportion to the diameter of the Pupil,
is strongly illustrated by the following cir-
cumstance. — " What can be the reason," a
very intelligent and accurately observing
Artist said to me, who was sitting by the side
of his window, " that when I look at that por-
trait opposite to me, it looks Warm with my
left Eye, and Cold with my Right 5 i. e. with
my Left Eye, which is from the window, it
appears considerably brighter, than it does
when I look at it with my Right Eye ?"

I gave him a " Circumspector"] and desir-

* We can never be certain that an Object does now
appear to us of the same precise Colour of which it appear-
ed last Day or last Week : neither can our being insensible
to any change ever prove to us that the Colour is the same.
Not only different Persons may have different sensations
of Colours, proceeding from the different dispositions of
their optic nerves and Retinse, or from the different tinc-
tures wherewith their Eyes are tinged, but also the same
person may, from the same causes, see the same Object,
differently coloured at different times without being sensi-
ble of it; and experiments are not wanting, whereby it
appears, that the same object was seen of different colours,
according as it was viewed with the right or left Eye."—
Dr. Porterfield on the Eye, 8vo. 1759, Vol.1, p. 128.

t The Circumspector, or " Diagonal Eye-glass" is
a convenient assistant to a Portrait Painter, who wishes

it) -PRECEPTS FOR IMPROVING AND

ed him to attentively examine the size of the
Pupil of each Eye while his head remained
in exactly the same position — and tell me in
which Eye the Pupil was largest : his answer
was, " Why, in the left certainly," i. e. in the
Eye least exposed to the Light.

Mr. Butt, of Bath, informed me that he
saw the Five first discovered Satellites of Sa-
turn in an Achromatic Telescope of 44 inches
focus, and 21 inches aperture — by placing a
patch before that part of the field of the Tele-
scope where Saturn appeared — and thereby
enabling the Pupil, to expand, and the Eye to
adjust itself for discerning the fainter objects,
the Satellites.

In observing Double Stars, the very minute
Star which accompanies some large Stars,
(for instance the small Star near Alpha Lyra)
is visible when the large Star is out of the
field — with a Telescope with which it is not
discernible, while the larger Star is stimula-
ting and shutting up the Pupil.

These very striking Facts, sufficiently es-
tablish the position laid down in the com-
mencement of this Chapter — that " cceteris

to catch a likeness unobserved, and wh ; ch is perhaps the
only W3V of obtaining the true natural expression of a
Countenance — and is also an invaluable Orarle for a fair
Lady to refer to, to adjust the irresistible Artillery of her
Eyes and Smiles.

PRESERVING THE SIGHT. 77

paribus" the impressions on the Retina, are
vivid, in proportion to the expansion of the
Pupil.

These observations led me to consider how
beneficial it would be to the Eyes of Paint-
ers, Pngravers, and those artists whose Eyes
are irritable from great exercise, if they could
be so shaded, that the Pupil might be secured
from being interrupted in its adjustment.
For which purpose I recommend a shade
made of black silk stiffened with wire, and
fixed on a Spectacle frame something like
the contrivance of Tubes* which are made
for viewing Pictures; such assistance to the
Sight — is surely quite as advantageous to the
Artist to paint with, as it is to the Amateur
to examine his Picture with.

The Eye cannot adjust itself perfectly,
while it is exposed to the stimulus of surround-
ing Objects — a defence from the intrusion of
collateral rays will prevent the picture on
the Retina being confused by those adventi-
tious rays which otherwise distract if ; and
if only those rays are admitted into the Eye
which come direct from the object under ex-

* See an Account of the great advantages of Spectacles
with Leathern Tubes, in the 3d vol. of the Phil. Trans.
for the year 1668, p. 727 and 765; aad for 1634 in Vol,
XIV. p. 474.
7 *

78 PRECEPTS FOR IMPROVING ASD

animation, it will make a much more vivid
impression on the Sight, which will be sharp-
ened and strengthened very much.

This is worthy the attention of all who
wish their Eyes to enjoy the utmost sensibili-
ty that they are capable of being excited to
— because,

The action of the Eye is perfect in the pro-
portion that its adjustment is perfect — and
when all its attention is concentrated on one
object, the sensibility of the Sight is much
increased ; — moreover, you will not only see
better, but Vision being rendered easier, your
Eyes may be employed longer, with com-
paratively less fatigue.

The Pupil of the Eye is larger when sha-
ded by a Broad Brimmed Hat — such as Coach-
men wear, who probably adopted thi> cos-
tume from its advantage in sharpening their
sight.

There is no part of the Economy of the
Eyes more important, than that the object
they are at work upon should be placed at
exactly that distance from them at which
they see with the greatest ease : — this may
he easily accomplished by the assistance of
A Double-rising Desk :

PRESERVING THE SIGHT. 79

and hard Students will do wisely to have a
High Desk at which they can occasionally
stand — instead of always sitting.

Those who are ranch occupied in Engrav-
ing — Painting — Writing — Reading — &c. or
works which require all the power of the Eye
to be exerted to the utmost — should be care-
ful not to offend it by too much Light, which
is quite as prejudicial as too little Light,

Light enough to illuminate the object, and
to make it easily and perfectly visible, is all
that is wanted : — on this occasion, the Old
Proverb, " Enough is as good as a Feast,"
is quite true, — more, is not only unnecessary,
but injurious, and will not only over-stirnulate
the Eye — and force the Pupil to shut itself

80 PRECEPTS FOR IMPROVING AND

up, but if continually so irritated, the Eye
will soon become as much impaired by such
over-stimulation, as the Stomach is by Dram-
drinking.

1 have observed in my visits to a numer-
ously attended Reading Room— that the seats
next the windows were generally filled by
persons wearing Spectacles, who had no doubt
accelerated the necessity for so doing by a
habit of over-stimulating their Eyes with su-
perabundant Light.

The proper way of defending the Eyes from
too much Light, is by preventing all that is
superfluous from entering the Room, by means
of Blinds or Shutters — thus, you may admit
only just such a degree of Light as you find
most agreeable to your Eyes.

All Artists choose a Room lighted only from
one aperture — and if possible with the steady
North aspect ; that is the best place in
the room, indeed the only proper place for
Study for those who have any regard for
their Eyes, where the Light falls on their
work or book — coming from the side or from
behind.

" It is requisite always to have an equal,
well regulated Li^ht in every employment,
particularly in the Evening; the Eye may
be seriously strained and injured by work-

PRESERVING THE SIGHT. 81

ing, writing, or reading with either too much
or too little Light : for want of a due atten-
tion to preserve the visual organ, and from
using the Eyes very much during the busy
part of life, a morbid sensibility is brought on,
an unnatural weight of the Eye-lids, a great
deficiency of distinctness, and occasionally
a distressing, undulatory quivering appear-
ance of refrangible colours on either side.
To remedy this, washingthe Eyes with clear
cold water, and keeping theo> from the Light
for an hour, or taking a Nap, will be found
most efficacious." — S. Pierce.

If your Eyes are much employed in Read-
ing, &c. and are extremely irritable, you
may have your window glazed with Green
Glass, — or a blind of it to put up occasionally
— or a rolling blind of Green Silk or Muslin
— or have a plate of Green glass fixed in a
Frame, which may be placed so that the
Light may pass through it to your book or
work. But do without ail these if possible
— for if they alleviate the irritation while
you use them — they will render the Eyes
more morbidly irritable after.

At Night — use a Reading Candlestick or
Lamp with a shade to shield the Eye from
the glare of the Light ;* which is of much

* Every thing is best seen when the light of the candle is

82 PRECEPTS FOR IMPROVING AND

t greater assistance to the Sight than those who
have not tried it can imagine : One candle so
shaded will enable a person to see better
than Two without such a shade, and with a
Cumumbra Lamp — you may see I think al-
: most quite as well as by Day-light, — the
sensibility of the Eye is preserved in such
perfection.

The Optic Pupil inevitably adjusts itself
to the brightest object, which therefore should
be that which it is its business to attend to, —
not the flame of a Candle, — but the Book
you are reading.

Green, or any Coloured Glasses, veil ob-
jects with a gloomy obscurity, and can never
%. be recommended, except to those who have
to travel over a white sand, or are much ex-
posed to any bright glare, — which cannot be
otherwise moderated.

Light reflected from any white surface, is
very piquant and injurious to the Sight, whe-
ther proceeding from Water — Snow, &c.

Gogglers — or black cups, glassed with plain

glasses, and mounted in double-jointed frames

* formed to the shape of the face — are pre-

jntercepted : the bright light of the Candle not only makes
the pupil contract, but by mixing itself with the images of
other objects, it in some measure obliterates them,. so as
they cannot be so well perceived." — Dr. PoRTERFlELD on
the Eye, 8vo. 1759, Vol.11, p. 188.

PRESERVING THE SIGHT. 83

ferable to those which are fixed in Leather
and Silk and tied on with riband ; the latter
come so close to the face that they soon be-
come a Vapour Bath for the Eye — but the
former are occasionally found very service-
able to travellers to protect their Eyes from
Wind and Dust, and to shield* them from a
strong Reflected Light ; Blue or Green glass
may be fixed in them, but it must be of, a
very light Colour.

Some more nice than wise folks, among
other ridiculous refinements have recom-
mended thin Green-Gauze or Crape, instead of
Green Glass — under the pretence, that while
it moderates the Light, that it still admits the
Air, and is, therefore, cooler to the Eyes.

All Coloured Glasses increase the labour of
the Eyes, and soon bring them into such an

* <{ Xenophon relates that many of his Troops were
blinded by the strong reflection of the light from the Snow
over which they were obliged to maich.

" Dionysius the Tyrant of Sicily, among other means
which he took to gratify his revenge, and satiate the savage
cruelty of his Temper, was accustomed to bring forth his
miserable Captives from the deepest recesses of the darkest
Dungeons, into white and well lighted Rooms, that he
might blind them by the sudden transition from one extreme
to the other.

" Actuated by principles equally barbarous, the Cartha-
ginians cut off the Eye-lids of Regulus and then exposed
him to the bright rays of the Sun — by which he was very
soon blindedj" — G. Adams on Vision, Svo. 1789, p. 8.

84 PRECEPTS FOR IMPROVING, &C

irritable state as unfits them for all the ordi-
nary purposes of Life : — there is scarcely
an external or internal Sense, but may be
brought by extreme indulgence, to such a
degree of morbid delicacy and acuteness, as
to render those organs which nature intend-
ed as sources of gratification — the frequent
sources of Disappointment and Pain.

The most proper material for Spectacle
Glasses, is that which shews objects the near-
est to their natural Colour.

Lastly — Whatever Glasses you use — take
care to " keep (hem perfectly clean ;" this is as
important, as the choice of the Figure or the
Colour of them*

Every time you wipe your Spectacles you
scratch them a little, and " many a little
makes a mickle" — therefore, when you have
done using them, put them away carefully in
their case, to prevent other people abusing
them — as a Naughty Boy did his Grand
Pa's Spectacles — who took the Glasses out —
and when the old Gentleman put them on-
finding that he could not see, exclaimed,
" Marcy me, Pve lost my Sight !" — but think-
ing the impediment to Vision might be the
dirtiness of the Glasses — took them off to
wipe them — when not feeling, them, he, still

GLASSES, &C 85

more frightened, cried out, " Why what's
come now, why I've lost my Feeling too !"

CHAPTER XIII.

GLASSES FOR SHORT-SIGHTED PERSONS.

I have met with several persons of 30 and
40 years of Age who had no notion that
thej were Near-sighted, until they accident-
ally looked through my Spectacles at a dis-
tant object : when thev exclaimed with sur-
prise, " Bless me, how clearly I see ! I never
saw any Glasses before, that I could see so
well with as with my naked Eye, and there-
fore had no idea that any Glass could im-
prove my sight."

" I can see to read a small print, as well
as any body I believe, bui 1 have sometimes
suspected that I did nut see any thing across
the street, or at a Theatre, quite so plainly
as I have heard other people say that ihey
did ; and I suppose that the Spectacles which
I tried before were not suitable to my Sight
-*-and so I hncl no idea that any Glass could
improve my Sight."

For such Eyes I have procured a No. 1, or
No. 2, Concave — and they have been delight-

8

86 GLASSES FOR

ed— and said, " Well, I see now that I have
ne^er before discerned the distinct outline of
any object which has been further than a few
feet from me."

Being a Short-sighted mortal myself, I
write this Chapter with confidence, from my
own experience of upwards of 31 years, and
hope to be able to give some good advice to
those who are unfortunately what is called '
Near-sighted — by briefly narrating " the His-
tory of my own Case of Spectacles."

I was about 15 years old, when I first dis-
covered that I could not discern distant ob-
jects so distinctly as people who have com-
mon Eyes usually do.

Mr. Ware, whose paper on Shortsighted-
ness I had not seen till after I had written
this Chapter, has remarked, (see Appendix])
that Young People seldom find out that they
are remarkably Short-sighted, until about the
time that I did ; which is true, and perhaps
for this reason, that Youns Folks seldom at-
tend to any thing in earnest before they at-
tain to that Age — when seeing, that I could
not see what persons with common Eyes fre-
quently pointed out to me as well deserving
my attention, I paid a visit to an Optician and
purchased a Concave Eye-glass No. 2.

.After using; this some little time, I acci-

SHORT-SIGHTED PERSONS. 87

dentally looked through a Concave No. 3, and
finding my Sight much sharper with this,
than with No. 2 — had my Spectacles glassed
with No. 3, which appeared to afford my Eye
as much assistance as it could receive.

After using No. 3 for a few Months, I
chanced to look through No. 4, and again
found the same increase of Sharpness, &c.
which I perceived before when I had been
using No. 2 and first saw through No. 3 —
therefore concluded that I had not yet got
Glasses sufficiently Concave, and accordingly
procured No. 4: — however, this soon became
no more stimulus to the Optic Nerve — than
its predecessors Nos. 2 and 3 had been.

I then began to think that the Sight is sub-
ject to the same laws which govern the other
parts of our System ; i. e. an increased Stimu-
lus by repetition soon loses its power to pro-
duce an increased effect — therefore, I refus-
ed my Eye any further assistance than it re-
ceived from Spectacles Glassed with No. 2,
which I have worn for upwards of 31 years,
and it is very nearly, if not quite, as sufficient
help to me now, as it was when I first em-
ployed it — giving me a Sight (for objects at
a moderate distance,) as 1 find, by compari-
son, about upon a par with common Eyes :—
without my Spectacles, I am quite as Sliort«

88 GLASSES FOR

sighted as some of my acquaintance who use
Nos. 6 and 7 concave ; i. e. we read at the
same distance.

Soon after I passed my 40th year I found
my Sight became rather Shorter as to distant
objects — and rather Longer with respect to
near objects — formerly, I usually wore Spec-
tacles for Reading, Writing, &c. — but lately,
the power of my Eye to adapt itself to vari-
ous distances is so diminished, that when I
read, &x. I am obliged to take off my Glasses
— and objects that are more than 70 feet from
me, 1 see better with one number deeper than
that T commonly wear. — See a similar case
in tire Appendix.

The gradations of Concavity, in the Con-
caves of the common Spectacles which are
marked Cheap in the windows of Sale-shops,
— Toy-shops, &c. — who pretend to undersell
the regular Opticians, {Read Chapter XIX,
and See the Appendix.) are not always work-
ed to a certain standnrd, and what one per-
son rails No. 5, another rates as No. 3, or 4,
or 6, or 7.

Mr. Pierce informed me that the late
Mr. Jesse Ramsden made the first No. of his
Concaves 10 be equivalent to a Convex of 24
inches focus, — t. e. if a Convex of that focal
length be united to a Concave No. 1 — the

SHORT-SIGHTED PERSONS. 89

combination will form a Plane, and objects
appear through it neither larger nor smaller
than they really are.

A 21 Inch Convex- - - No. 2.

An 18 Inch - No. 3.

and that all regular Opticians proceed in like
manner.

The following is a very important fact,
which the Short-sighted cannot be too fully
sensible of: —

" I shall mention a fact with which I was
made acquainted by Mr. George Adams the
late Mathematical Instrument Maker, who
was not only well skilled in the theory of
Vision, but, from his situation as an Artist,
had better opportunities than most persons of
learning such matters.

" The fact is this, that he does not know a
Short-sighted Person who has had occasion to
increase the depth of his Glasses, if he began
to use them in the form of Spectacles ; where-
as he can recollect several instances, where
those have been obliged to change their Con-
cave Glasses repeatedly, for others of higher
powers, who had been accustomed to apply
them to One Eye only."— Dr. W. C. Wells
on Vision, 8vo. 1792, p. 124.

The advantage of a pair of Spectacles, over a
Single Glass, is sufficiently obvious — as Ob-
g * '

90 GLASSES FOR

jects appear brighter when seen with Both
Eyes, than they do when viewed with One
only. — See Appendix.

For the Choice of Spectacles for Short-
Sighted Persons, — I have few Rules to offer
—it is a defect which has no reference to
Age — no stated progression that can be a
foundation to guide an Optician, or lead him
to recommend one Glass in preference to
another — but all depends on the observation
of the Short-sighted themselves — who I most
earnestly advise, to be content with as Shal-
low Concaves as possible — i. e. to take the
least Concave Glass through which they can
distinctly discern the names on the corners
of the Streets, and which gives a decided out-
line to objects whose distance does not ex-
ceed about 40 feet, and which renders them
clear, without making Vision dazzling and
glaring — the Glass which does, is too deep
by a Number. — See Appendix,

After your Eyes have been long accusto-
med to the assistance of Concave Glasses, the
smallest variation in the degree of their Con-
cavity will be extremely distressing and in-
jurious to the Sight : — when you have found
Glasses which exactly suit you — have Two
or Three pairs fitted to your Spectacles, that
you may be provided if a Giass gets scratch-
ed or broken.

SHORT-SIGHTED PERSONS, 91

Near-Sightedness generally continues the
same during Life, and precisely the same
Glass continues to afford precisely the same
assistance.

After persons have used the same glass for
some years — and it is broken, &x. it is often
extremely difficult to make them think, that
any new one suits their Sight exactly so well
as the Old one which they had been in the
habit of long using : therefore Pebbles are es-
pecially desirable for the Short-sighted.

Persons who are extremely Short-sighted,
to prevent their stooping in writing — to read
Music, &c. &c. may wear Spectacles with
very shallow Concaves, just enough to ena-
ble them to see such objects at the same dis-
tance which others do.

A Deeper Concave is wanted to see very
Distant Objects. Dr. Maskelyne,* the late

* (i When I look at the brighter fixed stars, at consider-
able elevations, through a concave glass fitted, as I am
short-sighted, to shew them with most distinctness, they
appear to me without scintillation, and as a small round
circle of fire of a sensible magnitude. If I look at them
without the concave glass, or with one not suited to my
eye, they appear to cast out rays of a determinate figure
not exactly the same in both eyes, somewhat like branches
of trees (which doubtless arise from something in the con-
struction of the Eye\ and to scintillate a little, if the air
be not very clear. To see day objects with most distinct-
ness, I require a less concave lens by one degree than for
seeing the stars best by night, the cause of which seems to

92 GLASSES FOR

Astronomer Royal, to look at the Constella-
tions, found it convenient to use a Concave
one degree deeper than he wore for common
purposes in the day time — and the Author
uses No. 2, in ordinary, but at NiVht sees
many faint Stars well with No. 3, which he
cannot see at all with No. 2. This is espe-
cially remarkable in the early part of the
Evening when the Stars first become visible.
And at Large Theatres, he finds one Number
deeper than that which he ordinarily uses is
a very advantageous indulgence to his Eye.

To give more assistance to the Sight to see a
distant object, many persons hold a Concave
Eye-Glass very obliquely to the Eye — in
which position, a Concave No. 3 will give al-
most the same sharpness of outline to objects
as No. 3§ when held parallel to the Eye.

For distant Objects, extremely Short-
be, that the bottom of the Eye being illuminated by the
day objects, and thereby rendered a light ground, obscures
the fainter colours blue, indigo, and violet, in the circle of
dissipation, and therefore the best image of the object will
be found in the focus of the bright yellow rays, and not in
that of the mean refrangible ones, or the dark green, agree-
able to Newton's remark, and consequently nearer the re-
tina of a short-sighted person ; but the parts of the retina
surrounding the circle of dissipation of a star being in the
dark, the fainter colours, blue, indigo, and violet, will have
some share in forming the image, and consequently the
focus will be shorter."— See Phil. Trans. Vol. LXXIX.

SHORT-SIGHTED PERSONS. 93

sighted persons should use a small Opera-
glass, which having an adjustable focus, if it
only magnifies Twice,* will be infinitely bet-
ter than any single Concave, because h can
be exactly adapted to various distances.

My u Invisible Opera-Glass" a contrivance
of Mr. Pierce and myself, is a great acquisi-
tion to Short-sighted Persons, and is an ines-
timable little Instrument for Artists, &c. who
wish to discern the distinct outline of objects
at short inaccessible distances ; i. e. for an
Architect to see the exact outline of a Build-
ing a furlong off — or to examine the point-
ing, &c. of the walls of upper stories, &c.

When shut up in its case, this little Glass
is only 2 inches in length ; — when in use,
about 3 inches : — it has a single piano-convex
Object-glass ^ of an inch in diameter, and
its Magnifying power is about 3 times.

There is a very general Vulgar Error, that
Short-sighted persons who use Concaves, as
they get Older, become less Short-sighted :

* An Opera-Glass which only magnifies once, like the
fashionable Grand Dandy Operas — of which the Eye-glass
is as large as the Object-glass — is of no use to a Near"
sighted person ; — who, to receive the same benefit which a
common Eye does, will require rather more magnifying
power : — A very short-sighted person will receive^very lit-
tle more assistance from an Opera-giass which magnifies
Twice, than a person with a Common Eye will from one
which magnifies Once,

94 GLASSES FOR

on the contrary, every Optician and Short-
sighted person that I have consulted on this
subject, have assured me, that as their Eyes
become impaired by Age, to see distant ob-
jects sharp and distinct, they require rather
deeper thnn shallower Concaves ; and at a
very advanced Age, sometimes complain
that they cannot see to read so well as for-
merly, and require Convexes of 36 or 30 in-
ches focus.

Mr. Pierce informs me, that Dr. Parker,
the late Rector of St. James's, Piccadilly, had
from his youth a short-sight, and when al-
most four score years of age, complained to
him that he could not read so distinctly as
he wished : with the help of Convexes of 36
inches focus, he was enabled to read and
write with comfort to himself for several
Years after. — See Appendix.

That a Short-sight is stronger and better,
and more lasting than a Common-sight — I
have always set down among the most ab-
surd of Vulgar Errors — unless, to be half
blind all their Life, as the Short-sighted are,
is better than to be so only during about one-
third of it, and that during the latter part of
Life, as common Eyes are.

This prejudice is as foolish as the silly no*
tion some people have — that a severe fit of

SHORT-SIGHTED PERSONS. 95

Gout, is a thing to give a man Joy of —
which our philosophical poet. Pope, admira-
bly illustrated when he said : —

'* So when small humours gather to a Gout,
" The Doctor fancies he has driven them out."

Lssay on Man.

If the observations of Lord Chesterfield
and Dr. Reid are true, a Short-sighted Per-
soil without Spectacles, is under a sad disad-
vantage in the common business of Life. —
The following is the advice this keen obser-
ver of Human Nature gave to his Son : —

" Mind not only What people say, — but
How they say it : — if you have any sagacity,
you may discover more truth by your Eyes
than by your Ears. People can Say what
they will, but they cannot Look just as they
will ; and their Looks frequently discover
what their Words are calculated to conceal."
— See Letter 77.

Dr. Thos. Reid's observation on the Eye
is — " Of the faculties called the Five Senses"
Sight is, without doubt, the noblest : by
means thereof we can perceive the tempers
and dispositions, the passions and affections
of our fellow-creatures, even when most they
want to conceal them : and when the Tongue
is taught most artfully to lie and dissemble,
the Hypocrisy appears in the countenance

96 SPECTACLE TRAMES.

to a discerning Eye ! and we can perceive
what is straight and what is crooked in the
Mind, as well as in the Body." — Inquiry into
the Human Mind, 8vo. 1818, p. 140.

EJowever, it is some consolation to the
Short-sighted, to consider, that if the natural
infirmity of their Eyes prevents their enjoy-
ing this advantage, the use of Spectacles not
only enables them to see what is passing in
the Eyes of others, but that they form a veil
over their own, which, in a great degree,
prevents any such Scrutiny ; and thus—their
Weakness becomes their Strength.

CHAPTER XIY.

SPECTACLE FRAMES.

I prefer a well-hammered Silver Frame
with Double Joints, the Second joint of
which may be turned on its pin over the
First, so that, they may be occasionally used
with the Single joint only — they sit close and
steady on the Head, and are convenient to
wear under a Hat— do not press either on
the Nose or on the Temples — but their pres-
sure is general and equal, and as it may be
varied, may be rendered more agreeable
than any other Frame.

SPECTACLE FRAMES. 9?

Spectacles with only a Singh Joint, must
press hard somewhere.

Tortoise-shell Spectacles have a gloomy
heavy appearance, are no lighter than Sil-
ver ones, and are very easily and very often
broken :— -however, if you will have a Shell
frame, let the front be all Black— variegated
Shell is bad for the Eye.

The Blued Steel Frames are good looking
enough when new, but soon lose their Azure
lustre, and then look very shabby : there is
a prejudice in favour of a Steel frame as
being very light, — and, from its elasticity,
that its pressure on the Head is less {han
that of a Silver frame. — It may be for the
first fortnight; but in the course of that time,
such is the ductile nature of a Silver frame,
which soon adapts itself exactly and com-
fortably to the Head, and becomes infinitely
easier and pleasanter than the Springy Steel ;
and the truth of the old saying, " as easy as
an Old Shoe," is remarkably felt in " an
Old Silver Spectacle Frame."

That the Frame should be Light, is the
only point which either the Makers or the
Wearers of it seem to pay any attention to —
and to Lightness, every other property of it
is willingly, but ridiculously sacrificed.

The actual difference in Weight between
9

98 SPECTACLE FRAMES*

a Silver Front of that proper decree of
strength which I have recommended, and
one of the silly flimsy fronts which are com-
monly so much admired, does not exceed
Four Pennyweights,

Let the Frame be large enough not to
press on the Head, or Head-aches, fyc. fyc.
will be the inevitable consequence.

The Length of the Bridge, i. e. the dis-
tance between the Glasses, must be regulated
by the distance between the Eyes, and the
Centres of the Glasses must come exactly
before the Centres of the Eyes ; — according to
the coincidence of which, Vision will be
perfect or imperfect.

The mean Distance between the centres of the
Pupils of the Eyes of People in general, is
about Two Inches and a Half.

The following are the usual proportions of
Spectacle frames.

The Length of the Bridge, from an Inch to
an Inch and y^ths.

Of the Openings which hold the Glasses, if
they are Oval, the longest diameter should
not be less than an Inch and T Vh, the Shorts
est about T yhs.

The Length of the Common Knuckle is about
T ^ths of an Inch : — in some peculiarly formed
Faces, this must be wider, and in others nar-
rower.

SPECTACLE FRAMES.

99

The Length of the Knub Knuckle (which is
decidedly the most elegant) is only T V ns °^
an Inch.

' THE WIDTH OF A COMMON FRAME.

Bridge ......

Openings for the Glasses
Rims of ditto ....

Common Knuckles . .

Inches.

Tenths

1
2

1

4
2
8

4

5

See Figure in the Plate fronting the Title.

To assist the Optician to ascertain exactly
what ought to be the breadth of the Bridge, — 1
recommend him to have a trial Frame, with
an adjusting Bridge which will separate half
an Inch — and such separating part graduated
1. 2. 3. 4. 5. for each T yh of an Inch — put
these on, and adjust them till the centres of
the Glasses come exactly before the centres of
the Eyes,

If his Frames are numbered 1. — 2. — 3. —
4. — 5. according to the width of the Bridge
— the Eyes of his Customers may be imme-
diately suited to a nicely.

The Form of the Bridge must be regulated
by the Form of the Nose which it is to cross.

The closer the Glasses are brought to the
Eye the better, provided they do not come

100 SPECTACLE FRAMES.

so c'ose as to be touched by the Eye-lashes
if they do, the Glasses will be continually
dimmed by the moisture from the Eye-lash-
es ;* and what is worse, the Eyelids will
become irritated and inflamed.

In the course of time Spectacle frames get
out of proper shape, and become too loose
to keep the Glasses up to the Eyes : — this
arises so imperceptibly, that I have found it
occur to several persons who were uncon-
scious of it. — The Optician easily remedies
this, by restoring the bend of the Sides to
their original form, and new pinning the
Joints of them.

Nothing can look more ridiculous, than the
trick which some Idle persons have, of sus-
pending their Spectacles on the very tip of
their Nose : — this is as injurious to their own
Eyes, as it is absurd to the Eyes of others.

The Bridge of Spectacles for Long-sighted
Persons, who wear them to read with, is best

* The quantity of Tears spread over the Globe of each
Eye in the space of 24 hours, amounts to Two Ounces and
upwards; i. e. a common sized wine-glass full. — People
who make use of Spectacles have opportunities of observing,
that the evaporation of Tears tarnishes very much the
Circles which surround the Glasses. — Dr. P. Degravers,
on the Eye and Ear, 8vo. 1800, p. 116. Surely the subject
on which the Doctor made this experiment must have been }
< £ like Mobe all Tears,"

SPECTACLE FRAMES. 101

t>f the form, (shewn in the Plate) which when
the Eyes are employed in Reading or Work-
ing, &c. brings the Glasses parallel to the
centres of the Eyes.

For Short-sighted Persons, it should be
straight — because the Glasses are required
to be parallel to the Eyes when you look
straightNforwards horizontally.

The proper Shape for the Openings which kold
the Glasses, is the true regular Oval* — which
form is similar to the Opening of the Eye. —
"The Vulgar opinion is, that Circular Eye
Glasses are ground of the most perfect Figure -
— the Fact is, that the Oval Eye Glasses are
ground Round at first and then clipped Oval.

The Front of the Frame- should project be-
yond the Glasses far enough to protect the
Glasses when people carelessly lay them
down on their surfaces — and also to prevent
their being injured by rubbing against the
Case, when passing in or out thereof.

The Front must be Strong enough not to bend %
in the smallest degree — or the Glasses will lose
their parallelism with the Eyes, vision will
be distorted, and the Sight distressed.

* Spectacle frame-makers complain that the Glass grin-
ders have a barbarous custom of distorting their Ovals, by ♦
putting in ill-shaped Glasses — and forcing the openings to
adapt themselves to them.
9*

102 SPECTACLE FRAMES,

The whole of the elasticity of the Frame
* must be in the sides.

Th,p First Joint should be of Silver wire of
the Jyh of an Inch in Diameter, and Four
Inches and a half in length, and so curved as
not to touch the Head except by the last half
inch of it. The First Joint is seldom more
than 4i inches in length — but the apparent-
ly trifling addition of a quarter of an Inch in
its length gives it a much more steady and
comfortable attachment to the Head, than
can be imagined by those who have not tried
it— especially when the Second Joint is turn-
ed down and you use it with the First Joint
only.

The Second Joint should be flat, about the
•Jth of an Inch in breadth, and 21 Inches in
length, with a loop end — and the Pin which
* fastens it to the First Joint should be kept
tight enough to preserve the Second Joint in
whatever position the wearer finds easiest and
most convenient. — If this becomes loose — it is
easily tightened by placing the pin on which
it turns, over a piece of Iron and giving it a
gentle tap.

Mem. — If the Pin which fastens the Second
Joint to the First is not rivetted very nicely
and smoothly — every time You takeoff your
Spectacles, you will find it an Infallible De-

SPECTACLE FRAMES. 103

pilatory— and if "Time has not thinn'd your l
flowing Hair," your Second Joint very soon
will.

N. B. If the Second Joint be turned up-
wards to an Angle of about 30 degrees, it I
will be in the best position for preserving
the Frame in its proper place.

PRICES OF SPECTACLES.

L. s. d.
Best double-jointed silver Spectacles with

Glasses 1.10

Ditto with Brazil Pebbles 1 16

Best single joint silver ditto with Glasses „ 13

Ditto with Brazil Pebbles 18

Double joint Steel ditto with Glasses ..050

Single joint ditto .036

Ditto 026

Morocco Cases 16

Double-jointed Hand Spectacles in Pearl .

CHAPTER XV.

OF THE QUALITY OF SPECTACLE GLASSES, AND
HOW TO MEASURE THEIR FOCAL LENGTH.

The defects of Spectacle Glasses are either
from Veins — Specks — Scratches- — Colour —
or false Figure.

1st. To discover Veins in a Convex Glass
place a Candle about 5 or 6 yards from you ;
then look through the Glass, move it from

204 SPECTACLE GLASSES*

3^our Eye till you find it full of Light, and
you will then clearly see every vein 9 &c. in it
which renders Vision imperfect by distort-
ing the Objects.

2dly. Specks or Scratches are not so mis-
chievous as Veins — for they do not distort
the object, but only intercept part of the
Light ; — however, such defective Glasses will
not be used, except by such persons who
think that their Two Eyes are not worth
Two Shillings.

3dly. False Figure. To prove the Figure,
lay a Book before you, hold the Spectacles
in your hand, and looking through them re-
move them gradually from the Book. If the
figure of the Glasses is false, the objects will
appear distorted and confused. Thus if you
view any cross lines which form small squares,
through a falsely ground glass — some of the
squares will appear with strait sides distinct
and all of a size ; others with crooked sides
of different sizes and confused ; so that the
whole will be neither like the original, nor
all parts of it distinct at the same distance.

If you view it through a true glass, it will
be exactly like the original figure and uni-
formly distinct, only magnified according to
the degree of the power of the lens used ;
and as you gradually remove the Glass be-

SPECTACLE GLASSES. 105

yond the focus, if you take care to move the
Glass perpendicular to the plane of the Pa-
per, all parts of the object will become equal-
ly indistinct at the same distance.

4thly. The Colour of the Glass — That is the
best material for looking through, through
which Objects appear nearest to their natural
Colour — the easiest way of examining the
Colour of a Glass is to lay it upon a piece of
White Paper.

To MEASURE THE FOCAL LENGTH OF SPEC-
TACLE Glasses. — The usual manner of mea-
suring the focus of Spectacles, is to hold them
opposite a window against the side of a room,
and draw them gently away forwards un-
til the frame of the window can -be seen,
making a small image through the Specta 1c
glass on the Wainscot or Side of the room.
When the window frame .appears most dis-
tinct, thp number of inches, measured by a
rule between the glass and the wall, or par-
tition opposite, will shew the real focal length.

10€ PEBBLES,

CHAPTER XVI.

PEBBLES.

Some folks have a notion, that " Pebbles
are much cooler to the Eyes than Glasses :" — -
the relationship between " a Pebble" and
" a Stone" and the Proverb " as Cold as a
Stone" probably gave rise to this prejudice
in favour of Pebbles.

It is quite impossible to distinguish between
good Pebbles and good Glasses.

People call that Glass coolest to the Eye,
which is of the most proper focus for it, and
which therefore irritates and fatigues it the
least — and through which they can see easi-
est and best.

The only superiority of Pebbles over Glas-
ses is, that they are not so liable to be bro-
ken ; and as they cannot be scratched by
any thing softer than a Diamond, they may
be carried in the pocket without a Case;
which are certainly great advantages, espe-
cially to Travellers and Short-sighted Per-
sons— (See page 100) but I must warn my
friend the Reader that Pebbles are so very
veiny, that it is seldom a bit is found so per-
fect as it ought to be, and therefore 1 pair of

GLASSES FOR SPECTACLES. 107

the Best Pebbles cost 16s. i. e. as much as B
pair of the Best Glasses.

OBSERVATIONS ON THE MATERIALS AND MAN-
UFACTURE OF GLASSES FOR SPECTACLES.
By Mr. S. Pierce, Optician.

The best material for the formation of
Spectacle-glasses, is the White Plate, common-
ly termed Dutch Glass;* it is very clear and
hard, without veins or specks comparatively,
and bears an excellent polish : Crown-glass
is too dark and seedy for the purpose ;
French or British Plate is more difficult to
polish well, and Spectacle-glasses made there-
with are generally Grey ; that is, the fine
grinding from the Emery is not sufficiently-
polished off.

Much has been said to persuade the Public
that each Spectacle-glass ought to be ground
and finished singly by itself, else its defects
of variety of foci, incorrect representation of
objects, and false colouring, must be consi-
derable. But every one acquainted with
Glass Grinding, is well convinced, and will

* I am informed tha* th£ British Plate Glass now
made in East Smithfield, is very superior to any that was
formerly made in this country. — Editor.

108 GLASSES FOR SPECTACLES,

be ready to assert, that a Glass of so small a
diameter as an inch and a half, cannot possi-
bly be worked so steadily,- nor so true, by the
hand singly, nor polished off so fair and re-
gular, as when several are worked together
in a Block : this block may probably hold
four dozen of glasses, which are worked,
ground, and polished together in a tool of
an exact radius to produce the focal length
desired. The firmness of a Block of Glasses
secures you against the possibility of form-
ing any irregular sphericity, and gives it a
decided advantage.

Some years since, Spectacles were brought
from Holland, the glasses of which had been
heated sufficiently to receive a Concave or
Convex form, by being pressed in iron Pin-
cers or Moulds of various curvatures, without
any other process:— it is easy to conceive
that each Glass must have had an inequality
of foci, extremely injurious to the sight of the
unfortunate user, yet these vile glasses were
almost universal throughout France and Ger-
many.

In England it is no uncommon thing to find
the Spectacle-glasses of an itinerant optician,
ground on one side only, while the other side
remains as it was originally cut out from the
plate, without being worked at all, and, more-

OF THE EYE AND EAR. 109

over, full of veins, &c. which refracting the
light irregularly — distort the object and dis-
tress and greatly injure the Eye, and are as
detrimental to the Eyes as the former ; but
the article is sold cheap, which is too often
the most tempting recommendation to the
million : but as a pair of the very best Glas-
ses, which are warranted free from all im-
perfections, may be purchased for only two
shillings — who would be so mad as to run
the risk of forfeiting the fee simple of his
precious Sight — for four-and-twenty pence!
for a Groat a Year ! ! for the Glasses seldom
require changing oftener than once in half-a-
dozen years, and sometimes not in a dozen ! ! !

CHAPTER XYII.

ON THE VARIOUS DEGREES OF THE PERFEC-
TION OF THE EYE AND EAR.

Good, and well-educated Eyes are as much
delighted with the Harmony of Colours — as
fine Ears are with the Harmony of Sounds
— and a cultivated Eye is as much distressed
by ill-according Colours — as a cultivated Ear
is offended by discordant Sounds. I well re-
member that excellent Musician, Dr. Arnold,
10

110 VARIOUS DEGREES OF PERFECTION

telling me when I was studying composition
with him, that when he first began to learn
counterpoint, his Ears were so excruciated
by the Chord of the 2nd of the Key — i. e.
the Sharp 6th — that he used to call it " the
Gritty Chord."

It has been recorded that the Eyes of some
persons have been gifted with such Penetrat-
ing power (as Dr. Herschel termed what I
call Illuminating power) — that they could
perceive the Moons of Jupiter. — See G.
Adams on Vision, 8vo. 1 789, p. 64.

I have heard of, but never met with such
Visual organs.— Common Eyes can scarcely
perceive them with a good Achromatic Opera
Glass magnifying 4 times.

Father Castel invented an Ocular Harpsi-
chord — which w 7 as strung with coloured tapes
instead of wires, and being placed in a dark
room, when the keys were touched, the
transparent tapes which corresponded with
them became visible. C. published a pam-
phlet describing this curious machine, which
was translated into English, and I once had
a copy of it.

I have met with some very sensitive Ears
— and I have known several extraordinary
Musicians who have been able, if a handful
of the keys of a Harpsichord were put down.

OF THE EYE AND EAR. Ill

so as to produce the most irrelative combi-
nations — to name each half-note without a
mistake. — When I mentioned this to that ex-
cellent Organ Player, Mb. Charles Wesley,
he said, " At the age of twenty, I could do
it myself — but I can't now." He was then
in his 55th year.

The delicately discriminating power of the
Ear is more the gift of Nature than extreme
sensibility of the Eye, which latter is I be-
lieve always in a considerable degree the re-
sult of cultivation. — Miss Cubitt, of the The-
atre Royal, Drury Lane, when only six years
old, surprised me very much, by the high
degree she then was gifted with the former
faculty ; so was Mr. Watson, of the Theatre
Royal, Covent Garden: which they still re-
tain.

Mr. T. Cooke, the Singer and Composer
to Drury Lane Theatre, whom no one will
contradict me when 1 style the most extra-
ordinary Musician of the present Age, when
I put down the following Notes on a Piano-
Forte, — told me at once, " I think, Sir, that
you have Beef in one hand — and Cabbage in
tjje other.

112 VARIOUS DEGREES OP PERFECTION
D b Minor.

BE E F , CAB BAGE.

CAB BAG ^E, B E E F.

orG# Major.

"izir^H^-L

"CzCzt"Jjrda:3D

izztzpiz:«S!rftp.

Some Eyes are doubtless of as superior a
quality as these Ears.

But the other extreme is more common, of
the ears being so dull and badly provided
with defining powers, that their owners can
hardly distinguish " Oh the Roast Beef of
Old England" from " Buttered Pease ,-"— and
are more delighted with the discordant
screams of their Pet Parroquet, the snarling
of their Darling Dog— or some such Barba-
rous Uproar — than with the sweetest Melody
or the sublimest Harmony— Arne or Handel
ever imagined.

Sound passes through the Paste-board Par-

OP THE EYE AND EAR, 113

iy Walls of modern houses with such unfor-
tunate facility — that the majority of the
Dogs- — Parrots — Piano-fortes, &c. in this Me-
tropolis are — Actionable Nuisances ! ! !

I believe that many of those imperfect per-
formances, and erroneous opinions, which are
usually ascribed to the want of Skill, or the
want of Industry, or Good Sense — would be
more justly, and will be, set down to the want
of Good Senses by those who adjust the Micro-
scope of Criticism with Good-nature.

When I have heard the works of various
Artists, of Painters, Engravers, &c. found
fault with — for either bad drawing, or bad
colouring, or finishing, — I have often thought
that such defects, in construction or arrange-
ment, have been owing more to the Eyes of
the Artists riot being capable of shewing
them how to do better — than to the careless-
ness, &c. which they have been inconside-
rately censured for those who had a sharper
Sight. — A Good Eye, is unhappy, till every
part of its work is as perfect as it can make
it:— the gratification which it then receives
is so superior to all other considerations, that
to obtain it— Labour becomes Pleasure.

We find persons of profoundly Good Sense,
have imperfect notions on some subjects, to
10*

114 VARIOUS DEGREES OF PERFECTION

a degree which is quite surprising until ex-
plained on these principles.

Few men are " framed so in the prodigali-
ty of Nature," as to have all their Senses in
perfection — very few have a single One, that
approximates within many degrees of it-—
the Eye of Raphael, the Ear of Handel, — or
the sensitive Touch of the Blind Girl who
could feel Colours — are pancratic faculties
which are seldom produced."

The peculiar Genius and Character of
each Individual originates either in the ex-
quisite sensibility — or in the extreme obtuse-
ness of some single sense : — this makes one
man a Painter, — -another a Musician, — in op-
position to all the influence which can beset
up against it.

Many eminent Painters and Musicians
were originally self-taught, and unable to re-
sist the fascination of their Eve or Ear, but
were so overcome by their love of their Art
— that they have overcome all Obstacles,
which were placed in their way to prevent
them pursuing it.

I have met with persons in whom the sense*
of Seeing or Hearing was so absolute^ pre-
dominant, that— the other Four appeared to
foe totally eclipsed :

OP THE EYE AND EAR. 115

« And hence one Master Passion in the breast,
Like Aaron's serpent, swallows up the rest."

Pope.

Where Nature has given an extremely sen-
sible faculty to a man, the employment there-
of is more delightful and easy to him than
the employment of any other, and the culti-
vation of it, an irresistible enjoyment.

This is Genius in the proper sense of the
word, whether in Mind or Body — and is the
super-eminent faculty which is born in man.

The possession of extraordinarily Perfect
Senses, is by no means so enviable as people
ordinarily imagine, — the works which they
enable the possessors to produce can only be
fully appreciated by faculties equally perfect
and equally cultivated.

The purblind

" Undelighted, gaze on all delight."

The Sagacity to comprehend, and estimate
the importance of any uncontemplated im-
provement — is confined to the very few, on
whom Nature has bestowed a sufficient de-
gree of perfection of the sense which is to
measure it ; — the candour to make a fair re-
port of it, is still more uncommon — and the
kindness to encourage it — cannot often be
expected from those, whose most vital inte-
rest it is, to prevent the developement of that,
by which their own importance — perhaps

116 VARIOUS DEGREES OP PERFECTION

their only means of existence — may be for
ever eclipsed ; and as Pope says —

How many are

Condemned in Business or in Arts to drudge
Without an Equal — or without a Judge."

Thus, the Inferiority of the Senses of
others — prevents their deriving much advan-
tage from the Superiority of their own.

When Ability and Industry have over-
come the difficulties always attending the
perfect execution of exquisite works, they
have still to contend with the obfuscated
imaginations of the Ignorant, — and the mali-
cious misrepresentations of the Idle,- — the In-
terested,— and the Envious,— and are seldom
repaid for their exertions, unless they are
content to reckon with Pope, that

" One self-approving hour whole years outweighs
Of stupid starers, and of loud huzzas.
In parts superior what advantage lies !
Tell, for you can, what is it to be wise ?
'Tis but to know who little can be known,
To see all other's faults, and feel our own ;
Painful pre-eminence yourself to view
Above life, weakness, and its comforts too."

Pope.

Persons who have Bad Senses, i. e. only
just enough Ear and Eye to hear a Dinner
Bell, and find a Spoon — often appear to be
gifted with Good Sense in a very superior de-
gree, and seem to think deeper than those
who have the External Senses in greater

OF THE EYE AND EAR. 117

perfection. — When those avenues to the in-
terruption of Intellectual abstraction, the
Eyes and Ears,-— are half shut, — it is reason-
ble to suppose, that the Thinking Faculty
may be more active, and more perfect.

Those persons whose External Senses are
obtuse and imperfect, are generally, close
Reasoners — subtle Calculators — rigid Econo-
mists, — and in all respects Persons of exem-
plary Prudence.

The Insensibility, of people who have Bad
Senses, exempts them from many diverting
temptations, which assail those who See —
Hear — Feel — Taste — and Smell in perfection.

That Paragon of Good Sense — Dr. S. John-
son, was Short-sighted, and could not see dis-
tinctly more than 4 or 5 inches from him. —

His Ears were imperfect also, — when others
expressed the delight they received from Mu-
sic, he said, " I should be happy to have that
sense given to me ;" — and when a celebrated
Player had finished an elaborate Concerto,
which they told him was extremely difficult,
— he said — " Sir, I wish it had been impos-
sible."

The slovenliness of his own Dress, — I dare
say arose from the defect in his Sight, pre-
venting him from being sensible of the agree-
able impression produced by proper atten-
tion to neatness in others.

118 PANCRATIC EYE-TUBE.

We have irresistible evidence that his
Taste was defective, — for his appreciation of
a Good Dinner, was according to the Scale
which Tasteless people always measure by, —
the Variety, the Rarity, and the Costliness of
it, — for he needed not Dainties to excite his
Appetite ; that, we are told, was sharp enough.

THE

PANCRATIC EYE-TUBE,

INVENTED BY

WILLIAM KITCHINER, M.D. ,

Is applicable to Achromatic* and Reflecting
Telescopes of all Lengths, and also to
Microscopes.

[See an Engraving thereof opposite this Page.]

This Eye- Tube is applied to the Telescope
in the same manner as other Eye-tubes, and
is adjusted to distinct Vision by the same
Pinion Motion.

* Those in which the Errors arising from Colorific refrac-
tion, are corrected by the figure, position, and refractive
power of the Lenses which constitute the Object-glass.

^

v> S

nair

■

&§

NJ

^

s

I:

i

in
is
P

tio
po

PANCRATIC EYE-TUBE. 119

For the Lowest Magnifying power, the
Three Inner tubes must be shut up within
the Outer one ; — when the Magnifying power
is to be increased, the smallest of the sliding
tubes, A, must be drawn out to either of the
numbers engraved upon it ; care being taken
not to draw out any part of the other sliding
tubes, B and C, until the whole of the First,
A, is pulled out ; — the Second tube, B, may
then be drawn out to either of the numbers
engraven thereon ; and in like manner the
Third tube.

The numbers engraved on the Tubes, de-
note the Magnifying power of the Telescope.

To change the Power for any less power
than the one to which the tubes have been
drawn out, the reverse of the above-described
mode of proceeding must be observed ; — the
Largest tube must be returned first, and so
on, until they have been brought back to the
number required.

Each alteration of the Magnifying power will
require a new adjustment of the Pinion ; — as
the Magnifying power is increased, the dis-
tance between the Eye-glass and the Object-
glass must be diminished.

" It has long been known, that the Magni-
fying powers of Telescopes could be aug-
mented by increasing the distance between

120 PANCRATIC EYE-TUBE.

the two glasses next to the Eye, and the two
that are next to the Object-glass, to almost
double the power of the Eye-tube in its usual
form, i. e. from 30 to 55, This is the utmost
that Opticians have heretofore accomplished ; —
yet this variation is so desirable, that I think
it only requires to be generally known, to
be generally desired, both for Convenience
and Cheapness.*

" A few months ago, I saw an Eye-tube,
made by Mr. Cauchoix, with a scale of mag-
nifying powers from 25 to 73 ; but, upon
trial, I found that the vision was perfectly
good only between 35 and 45.

" My attention was strongly excited by
the idea of One Eye-tube effecting the whole
business of Magnifying; and after several
experiments, with the assistance of Mr. S.
Pierce, I combined lenses of such propor-
tions that they admitted of being separated
from each other so as to Magnify at one ex-
tremity, more than double what they did at
the other, the vision continuing uniformly
distinct.

* Before Mr. Jesse Ramsden invented, about 1785,
The Pipe-drawer for the Terrestrial Eye-tube — and chang-
ed the Magnifying power, by changing the two Glasses next
to the Eye — for which half Eye-tube he chargedj|10s.6d. —
for every change of Magnifying power, there was the in-
cumbrance and expense of another Eye-tube, costing 11. 1?,

PANCRATIC EYE-TUBE. 12i

" Having now done more than had been
previously effected, I brought it to You.
The approbation You expressed of what I
had done, so encouraged me, that I applied
unceasingly, determined to perfect the object
in view, which I have now accomplished.

" I beg to present to you the following
accurate measurement of the powers, and
faithful account of the performance of

" The Pancratic Eye-Tube, which I think
gives a better defined image of a fixed Star,
— and shews Double Stars decidedly more
distinct,* and perfectly separated, than any
other.^Eye-tube, and I hope will enable us to
determine the distances of these objects from
each other, in a more perfect manner than
has been possible heretofore.!

"This Eye-tube, when accurately made,
applied to an Achromatic of 44 inches focus,
produces, in the most perfect manner, every
intermediate degree of Magnifying power
between 100 and 400, either for Celestial or

* Especially in Achromatic Teleseopes, which are, what
is termed, a little over-corrected^ and the purple rays pre-
dominate : that is, when the focal length of the Convex
Lens, is formed rather too long for the Concave.

t This may, perhaps, be accounted for, from the greater
degree of the aberration arising from the extreme sphe-icity
of the lenses in other Eye-pieces which magnify so highly.
11

122 PANCRATIC EYE-TUBE.

Terrestrial uses — the Field* of Vision continu-
ing uniformly distinct.

" Therefore it is presumed, that the advan-
tage of my Pancratic Eye-tube over the
usual common Eye-tube, in variety of Mag-
nifying power, — convenience, — cheapness, —
and portability, — is as 300 to 1. — The cost
of a common Eye-tube is One Pound ; of the
Pancratic only Two Pounds, two Shillings.

" The tubes are graduated; every 10 de-
grees, thus, 100, 110, 120, up to 400.

" The change from one Power to another
may be made instantaneously, with the ut-
most facility and certainty, and the Observer
always knows exactly what Power he is
using."

[The above is an extract from Dr. Kitchi-
ner's Letter to Sir Joseph Banks, P.R.S.,
which was read at the meeting of the R. S.
on the 20th of April, 1820.]

Another is made, which is adapted for
Terrestrial purposes, Magnifying with an
Achromatic of 44 inches focus, from 55 to

* It may be said that Common Eye-tubes have rather a
larger field — but of what use is that part of the field "in
which objects appear distorted and fringed with Colour.

That, can only be considered the actual and useful field
of view, the Margin of which, is as perfectly distinct as the
middle of the field, when the Telescope is adjusted at an
object seen in the middle of the field.

DAY TELESCOPES. 123

200 times — and with a 30 inch from 40 to
160.

The power it zuill give to a Telescope, is
according to the focal length thereof, and is
easily found by the Rule of Three ; for in-
stance — if the Telescope be of 18 inches
focus —

If a Telescope of") ( what will one of 18
44 Inches gives \ \ Inches ?

18

440
55

44)990(22i the Magnifying
88 Power with an

18 Inch.

110
88

22
from 22i times, up to 88 — being as low a
power as is requisite for Land Objects — and
as high as is requisite to shew the Ring of
Saturn, — the Belts and Satellites of Jupiter and
several Double Stars.

If the Pancratic be applied to a Telescope
with sliding tubes, it is desirable, on account
of the great power it produces, that, it should

124 DAY TELESCOPES.

have an Adjusting Screw with a tooth and
pinion ; these are made separate from the
Telescope, and introduced between the first
and second sliding tubes.

The Advantage — of having All Powers in
One Eye-tube is sufficiently obvious.

In very Clear Days the Air is so transpa-
rent, that we can use a Power of 100 for
Land Objects, and on objects well illumi-
nated sometimes 150, as well as in some other
days we can a power of 50. Telescopes
act best when used in the same direction that
the Sun shines. — I have known good Teles-
copes condemned by trying them upon ob-
jects situated towards the East in the morn-
ing, or the West in the evening.

To have Perfect Vision — every Day, and
every Object, must have its appropriate de-
gree of Magnifying* power ! — this can only
be accomplished by the Paucratic Eye-tube.

On the 25th of March, 1819, Mr. Pierce,
the Optician, with a Pancratic Eye-tube
which made a 1 foot Achromatic magnify
80 times, perceived * Geminorum to be
double.

* " The Effective Power of Telescopes has a
considerable range of extent, — and can only be assigned — i
when the Object to be viewed is given." — Sir Wm, HER^
schel, in Vol. CV. of the Phil, Trans, page 294.

D0UELE STARS* 125

On the 5th of April, 1819, I shewed this
with a power of 70 to Mr. Win, Brockedon,
the Painter, and to Mr. Charles Turner, the
Mezzotinto Engraver in Ordinary to His
Majesty.

* Geminorum requires very little Illumi-
nating Power : I have shewn it to several
persons who did not know that it was a Dou-
ble star, with two 1 foot portable Telescopes,
with an Object-glass of the usual aperture of
1§ inch in diameter, to which 1 applied a
Pancratic Eye-tube, which gave a power of
70 times, and they described to me its
appearance very accurately.

1 have seen these two Stars with 230 in an
Achromatic Telescope of 28 inches focus,
and 21 inches aperture, (which was made by
the present Mr. Dollond for the late Mr. G.
Hodgson, at whose sale in February last I
purchased it,) like Two Shillings on a bit of
Black Cloth — See diagram facing page 118;
but in which, I beg to observe, that the
smaller Star is made rather too small in pro-
portion to the larger Star. See Sir Wm,
HerschePs diagram of Castor, as it appeared
in his 7 feet Newtonian with 460. in the
Phil Trans, for 1782.

$ Bob'tis, was observed on the 25th of May,
1819, by Mr. H. Browne, F.R.S. and my-
11*

126 DOUBLE STARS*

self, with an Achromatic Telescope of S^-ths
aperture, made by Mr. George Doll and,
F.R.S. With a Pancratic Eye-tube magni-
fying 270 the two Stars, were just as per-
fectly and as distinctly defined, and at about
the distance from each other, as represented
in the Engraving of the Pancratic Eye-tube fac-
ing page 118, without either rings or rays,
&c, around them. This was in an extreme-
ly fine clear evening — the air quite still — and
the star very near the meridian. The Blue
colour of the smaller star was remarkably
bright for so small an aperture — This Dou-
ble Star is very rarely seen perfectly distinct-
ly, in an Achromatic with a less Aperture
than 3-J, or in a Gregorian Reflector of less
than 5 inches, and a Power of 300.

Sir William Herschcl saw it in his 7 feet
Newtonian when its aperture was limited to
3§ inches; with 460 the vacancy between
the Stars was h a diameter of the smallest.
See Phil. Trans. Vol. 95, p. 42.

Well might Dr. Mask dyne say that " Te-
lescopes of Sir Isaac Newton's construction
perform most excellently in the M'muti® of
Astronomy, especially if small Apertures
and long Foci are made use of." See
Supplement to the Nautical Almanac for
1787, p. 42.

DUMPIES. 127

Magnifying power 7uhen required for observ-
ing Double Stars, is also more perfectly
effective in an Achromatic Telescope, in
proportion, as it is derived from a proper
degree of original power from the Object
Glass — the image of the Stars appears small-
er, and their separation greater.

I will here take the liberty to caution
those who hereafter may be crazy with the
Dumpy* Mania, that the convenience de-
rived from Telescopes being made short, (if
beyond a certain proportion,) is greatly more
than overbalanced, by the errors produced
by the great increase of the aberration of
Sphericity arising from the deep curves of
the excessively small Eye-glasses we are
obliged to employ — there is much difficulty

* This appellation was first given by Mr. Short, the
celebrated Maker of Reflectors, to a Telescope he made
for the Honourable Top ham Beaitclerc, of 6 inches aper-
ture, and which I saw in Colonel Huberts Observatory at
Highbury ; it was only 24. instead of the length he usually
made them, i. e. 36* inches focus. The instrument is
well known in the Optical World by the name of "Short's
Dumpy.'''

Mr. Tulley informs me, that this Telescope is still in
high preservation, and is now in the possession of Mr*
Allen, Plough Court, Lombard Street.

* See the Supplement to the Nautical Almanac for
1787, p. 39.

128 DUMPIES*

in getting deep Lenses well worked— and so
much more mischievous are the errors aris-
ing from any deviation from proper figure.

It is almost impossible to find an Eye-glass
so deep as even the T yh of an Inch focus,
that will give a well-defined image of a Star,
notwithstanding much deeper magnifiers are
useable in Microscopes.

Steady Stands are now constructed at a
very moderate expense, which make it as
easy to use a Telescope of 9 feet, as one of
3 feet in length.

Writing the above, reminds me of a con-
versation I had about 25 Years ago with an
eminent Optician of great experience : —

Kit. How much more convenient short
Telescopes are than long ones ! I have late-
ly bought a Dumpy.

Opt. Do you find it perform much better,
Sir, than Telescopes which are of the usual
length ?

Kit. No, it certainly does not perform
better.

Opt. Did you pay much less Money for it
then?

Kit. No, Sir — a great deal more.

Opt. Then I think, Sir, that You have laid *
out your Money very badly — I guess that
You have not got so good a Telescope foF

DUMPIES. 129

£30. as You might have had with half the
trouble to yourself and the Optician for
£20. — for You might have had the choice of
half a dozen Telescopes of the usual length,
and what does it signify whether the Tube is
2 or 4 feet long ? — a Stand that will carry
the one will carry the other; and remem-
ber, Sir, that Vision is better, and easier to
the Eye — in proportion that Magnifying pow-
er is produced by Eye-glasses of long foci. —
I am taking it for granted, Sir, that the In-
strument is employed for important scientific
purposes, when the first consideration is Op-
tical perfection. — However, I ask your par-
don, Sir, for speaking so plainly — perhaps
You purchased your Dumpy merely for a
Plaything ?

I have seen • Bootis, as distinctly as re-
presented in the diagram, facing page 118,
with a Telescope which would not exhibit a
glimpse of the small star which accompanies
Rigel, nor the small star near the Pole Star —
and other Telescopes which would plainly
shew the latter, but failed entirely at the
former.

Very few Instruments are so perfect, that
they will perform perfectly well on all Ob-
jects. — There is almost always, some false
light flitting about some part of the Image,

130 DOUBLE STARS.

and if a small Star happens to be in that
part, it is enveloped therein, and is

^ Invisible or dimly seen."

I do not call it seeing a Star Double, when
you can only now and then, fancy you can
perceive a faint glimpse of a little flitting
ghost of an accompanying Star, during fits
of easy transmission — but only, when the
apparent diameters of the Two Stars are as
perfectly round, well defined, and distinctly
separate, with a deep black division between
them : as they are delineated in the diagrams
in the plate facing page 118.

I have several times seen that very pretty
object, y Andromeda, with 1-foot Achroma-
tics, with an aperture of 1 and -Jgth of an
inch, and a Magnifying power of 35. In
these little telescopes, the smaller Star which
in larger instruments appears of a fine Blue
colour — for want of illuminating power, ap-
peared of the same colour as the larger
Star. The Blue Colour of the Stars accom-
panying this Star and e Bootis, becomes
vivid in proportion to their proximity to the
Meridian, and the Perfection and Illuminat-.
ing power of our Telescopes.

I must here caution the Novice, that He
must not often expect to see these extremely

DOUBLE STARS. 131

minute objects to the utmost advantage,* as I
have described them, when 1 saw them at
very favourable moments with very fine
Instruments — especially the Colour of the
Blue Stars, even when they are near to the
Meridian, and the Illuminating power of the
Telescope is in due proportion to the
Magnifying power, and the Instrument is Ex-
tremely perfect — unless the Air is very clear and
still — and every circumstance is favourable.}

* " For if there be any vapours moving and undulating
in the atmosphere, which often happens, though the night
appears clear to the naked eye, these will entirely destroy
the distinctness of the appearance : and it often happens
that the air in this respect, at least here with us at Kew,
will so suddenly and so totally alter, that the object will
appear very distinct and very confused afterwards in 3 or
4 seconds of time ; and the air is sometimes so very varia-
ble that objects will appear instantaneously to change,
from being very clear to be confused, and then to be clear
again. It will therefore be proper to accustom one's self
to the fluctuating appearances of some land-objects, seen
in the day time through the reflector ; lest the undulating
appearances of the planets in the night may deceive one,
and incline one to think this instrument does not succeed
so well as it is certain it will in a pure undisturbed Air." —
Dr. Smith's Optics, 4to. vol. ii. p. 366.

t " I have had recourse to my Journals to find how
many Favourable Hours we may Annually hope for in this
Climate.

"It is to be noticed, that the nights must be very clear —
the Moon absent — no Twilight — no Haziness — no violent
Wind — and no sudden change of Temperature ; — and it ap-
pears that a Year which will afford 90, or at most 100
Hours, is to be called a very productive one." I ! ! — Sir Wm.
Herschel, in page Si of the 90th vol. of the Phil. Tram.

132 DOUBLE STARS.

The Astronomical Amateur should be fully
aware, that such is the capricious and vibra-
ting state of the Atmosphere of this Country,
that many Evenings which seem to be ex-
tremely fine, when the Stars appear very
brilliant and dazzling to the naked Eye, are
quite unfit for Observation, and our best Te-
lescopes will perform but very badly.

Sir Wm. Herschel observes, that " Double
Stars require a great deal of good distinct
light ; or even with the best instruments, the
observer must not condemn either his instru-
ment or his eye if he does not discern them."

N. B. The apparent Diameters — and the
Distances of Double Stars* from each other, — ■
vary very much, — according to the different
states of the Atmosphere, — the Defining, — *
Illuminating, — and the Magnifying power of
the Telescope, and their proximity to the
Meridian.

* The Reader will find, in the 26th Number of The Jour-
nal of Science, edited at the Royal Institution, 1822, 24
fa Diagrams of Double Stars, by Mr. J. South, F. R. S.

In the Second Part of the Economy of the Eyes —
will be given Portraits of the Planets, and Diagrams of the
most remarkable Double Stars, as they appear in Tele-
scopes of various Magnitudes, with various Magnifying
powers — stating with how Low a Power and how Small a
Telescope, the Stars may be perceived to be separate, and
with What Power they are seen best.

NEWTONIAN DIAGONAL EYE-TUBE. 1 33

To avoid the painful position when observ-
ing Celestial objects when they are near the
Zenith, I have tried all the 9 different kinds
of Diagonal Eye-tubes, the respective advan-
tages of which I shall state at large in the
Second Part of this work ; I have only space
here to say, that 1 think that the best I have
was made by Mr. G. Dollond, and consists
of a Plane Speculum placed at an angle of
45 degrees between the Object Glass and
the Eye-glasses, and receives all the Eye-
pieces, and renders an Achromatic Refracting
Telescope as convenient as a Newtonian Re-
flector.

The light lost in the Reflection is scarcely
perceptible when observing fixed stars — the
position is not only pleasanter, but our organ
of sight is more perfect, when we look com-
fortably straight forwards — than it is in the
break-neck position required in observing
objects in a high Altitude without such as-
sistance. It may be urged, that a Prism
would bend up the rays with less loss than a
Speculum can reflect them — but in the latier
you have only one surface to get worked
truly, and it is no easy thing to obtain that
quite good* — in the former you have several,

* " I find more difficulty in correcting the figure of the
little plain piece of metal next the Eye-glass than one
12

1 34 NEWTONIAN DIAGONAL EYE-TUBE.

and the imperfections of the glass to contend
with into the bargain : — such is the intense
intrinsic brightness of the fixed stars, that the
inferior degree of vividness of the pencil of
rajs is, 1 play say, imperceptible.

" * Lyras, I surmise, has Light enough to
bear being magnified at least a hundred thou-
sand times, with no more than 6 inches of
aperture, provided we could have such a
power, and other considerations would allow
us to apply it."

See Sir Wm. Herschel, First Catalogue
of Double Stars in the Phil Trans, for 1782.

As Sir Wm. Herschel has remarked, "the
Newtonian, as usually constructed, is admi-
rably adapted for observation, for the Ob-
server always stands erect, and looks in an ho-
rizontal direction, though the Telescope should
be in a vertical position, and elevated to the
very Zenith." —

The position it was placed in by this in-
genious Astronomer is, perhaps, still more
convenient.

" My Eye-glass is mounted on that side of

would expect." — See Sir Isaac Newton's Letter in the
Phil. Trans, for 1672, vol. vii. p 4032 ; and Sir William
HerscheVs O'is. inOctob. 12, 1782, in page 44, of the Phil.
Trans, for 1795. — Messrs. Watson and Tulley have assur-
ed me that no figure is more difficult to make, than a per-
fect Plane,

NEWTONIAN DIAGONAL EYE-TUBE. 135

an octagon tube, which in the horizontal po-
sition of the instrument makes an angle of
45° with the vertical — having found by ex-
perience that this position, resembling the
situation of a reading desk, is preferable to
the perpendicular one commonly used in the
Newtonian construction — which has the capi-
tal advantage of rendering observations
equally commodious in all altitudes; and
you may therefore place the Instrument in
the meridian, and view the stars in their most
favourable position." — See Phil. Trans, for
1786, Vol. lxxv., p. 457—8.

I have no hesitation in saying, that in the
uncomfortable (and if long continued, pain-
ful) position required in observing objects
near the Meridian with any other Telescope
— no Half Dozen Observers, even if as ex-
perienced, and as expert and as indefatigable,
as the Immortal Herschel himself, could
have performed, what that incomparable Ob-
server achieved single-handed with his 7 feet
Newtonian.

When we wish to discern those delicate
and minute objects, which are the most in-
teresting exhibitions our Telescopes display
to us, and with the finest Instruments are on-
ly discernible with the most favourable cir-
cumstances, — we should be in a position of

136 NEWTONTAN DIAGONAL EYE-TUBE.

the greatest ease : no cramp or painful pos-
ture must distort the Body, or irritate the
Mind; — the whole powers of which must be
concentrated in the Eye.

Such is the sympathy between the various
organs of the human body, that we may as
well attempt to think accurately on two sub-
jects at the same time, as to use two Senses
at the same moment: — each must be used
alone, if we wish to give it a fair chance of
doing its utmost. — As Shakspeare has observ-
ed of Listening with such profound attention,
that " each other Sense was lost in that of
Hearing."

The Magnitude and Colour, of Celestial Ob-
jects, appear surprisingly different, to differ-
ent Eyes. — The same Evening, that with a
power of 180, the planet Jupiter has appear-
ed to me to be about an Inch and a half in
diameter, — a person, who observed it the next
minute, said it looked as big as the moon ; —
another, about Four inches diameter ; — and a
third, thought it did not appear quite so large
as a small Pea.

" It will be necessary here to take notice,
that the estimations made with one telescope,"
cannot be applied to those made with ano-
ther. Whatever may be the cause of the
apparent diameter of the Stars, they are cer-

i

DOUBLE STARS* 137

tainly not of equal magnitude with the same
powers in different Telescopes, nor of pro*
portional magnitude with different powers in
the same Telescope." — Sir Wm. Herschel,
in vol. 72 of the Phil. Trans.

N. B. The Reader is cautioned, that my
Pancratic Eye-tube, is composed of Three Inner,
and an Outer Tube, and that when all drawn
out, it is 14 inches and $ f hs in length ; — when
shut up, not more than 5§ inches ; — and that
when drawn out, the magnifying power is
Quadruple, what it is when the tubes are
shut up.

As 1 have no Interest in the sale of this
Eye-tube, I have stated my opinion upon it
— it is made by Mr. Dollond, and sold at
£2. 2s.— for £l. Is. more than the common
Eye-tubes.

On the old Plan Two Magnifying powers
cost £2. 2s. : with the Pancratic mentioned
at page 122, you have Three Hundred for
£2. 2s.

None are Genuine but those precisely answer-
ing the above description, and exactly resemble
the engraving opposite page 1 1 8, and have
the following inscription engraven on the
Outer Tube : —

" The Pancratic Eye-tube : Invented by
Ww. Kitchiner, M. D."
12 *

138 PANCRATIC EYE-TUBE.

This remark is necessary, because, Coun-
terfeits* are made with only One Tube — which
have only half the variety of powers the
Pancratic has, and consequently, magnify on-
ly Half as low — or Half as high as they
ought — such are only put to ordinary Tele-
scopes, for the reason we have stated, that a
low power is put to an ordinary Opera-glass.

But the Reader must not expect that every
ordinary Telescope which is fitted up mere-
ly for Terrestrial purposes, — will properly
carry for .Celestial purposes, extraordinary
high Magnifying Powers, — nothing like it ; —
nevertheless — such Telescopes may be per-
fectly efficient Instruments for the purposes
for which they are made, and perform very
well for Land Objects — there are plenty of
Good Day Telescopes, — but few Superlative
Star Telescopes.

To bear an uncommonly powerful Eye-
glass, for Celestial purposes, you must have
an uncommonly perfect Object-glass, and as
the difficulty of forming this, increases as
the magnifying power to be used with it in-

* To construct this Eye-tube perfectly, requires All care -
and excellent workmanship — the Lenses must be All of ex-
actly the right focus — All without any blemish — and the
Glasses and the Tubes containing them must be very truly
centered with regard to each other, and to the Object Glass.

DOUBLE STARS. 139

creases- — in like manner, the makers must be
rewarded for their trouble, — which is great-
er, as the Instrument must be adjusted at a
Fixed Star, — which is a much more elabo-
rate and Eye-teazing operation than the or-
dinary method observed with Day Tele-
scopes, of the defining power of which, a
Printed Paper is often considered a sufficient
criterion.

If I was an Optician, — I think that I would
almost as willingly — Waltz blindfold and bare-
foot among 9 Red hot Ploughshares laid at
unequal distances from each other, — as have
All my Telescopes tried by that truly trou-
blesome test a Fixed Star.

When a Telescope is perfectly adjusted, — -
a very trifling accident — will derange it so
as to prevent its properly defining a Star —
although it may not perceptibly affect the
brightness or distinctness of the vision of it
with any other object — not even with the
Planet Jupiter.

Before You condemn a Telescope because
it does not very nicely define a Star, — try it
several Evenings with several Eye-pieces,—
and let the Maker of it (trust it with no other
Person) examine whether it be in perfect Ad-
justment.

Defects in Eye Glasses are seldom suspect-

140 PANCRATIC EYE-TUBE.

ed — but, however perfect the original power
of the Object Glass or Speculum may be, it
will avail little, if one of your Eye Glasses is
veiny, &c, or not quite clean— or not exact-
ly truly centred to the Object Glass.— Sir
Wm, HerschePs Observation in p. 31, of the
95th Vol. of the Phil. Trans* is perfectly
true :—

" The best Eye-lens will give the least spu-.
rious diameter of a Star."

Not One Instrument in Twenty can be made
to give a neat Image of a Star with its whole
Aperture, — and not Two of Them will give
quite so perfectly well defined an Image with
the Whole Aperture — as when it is to a cer-
tain degree contracted.

I do not think that any Achromatic of 2t
inches Aperture, and 3i feet focus, can be
made to give quite so neat an image of a Star
with the whole of that Aperture, as a fine 5
feet of 3§ths Aperture will when it is limited
to 21 — I have never seen one that approxi-*
mated within some degrees of it.

The more perfect vision in the 5 feet, I
am aware, is partly to be attributed to the
greater original power of its longer Object-
Glass, and to its larger Eye Glasses — but
what I have asserted is true of Telescopes of

DOUBLE STARS. 141

equal length ; though the improvement is not
in so high a ratio.

Whatever inexperienced Amateur Opti-
cians may think of this declaration of " the
Cook's Oracle" — 'tis true.

The Author respectfully assures the Reader
that these Lucubrations from his Garret-— are
the result of actual experiments; and, like
those which were lately published from his
Kitchen — are faithful statements of facts re-
peatedly proved.

Although he has been very cautious, in
constructing every sentence with words which
would express his meaning as exactly and as
clearly as He could, — nevertheless, — his
chief Ambition has been t© give those who
may do him the honour of perusing this lit-
tle Book, all the Information he has accumu-
lated, in the most convincing and most satis-
factory manner ;— and be has never been
contented to offer a mere assertion, whenever
it has been in his power to produce collate-
ral proofs from the writings of experienced
authors.

" If the Aperture of a Telescope be 5 or 6
inches, there will be required a piece of Me-
tal 7 or 8 inches broad at least, because the
figure will scarcely be true to the edges."
See Sir Isaac Newton's Letter to the Secre-

142 PANCRATJC EYE-TUBE.

tary of the Phil. Trans. March 26, 1 672. vol.
vii. p. 4032.

It may be supposed that Speculums are
now worked with more accuracy than when
" the Optician's Oracle," Sir I. Newton, wrote
the above ; however, I have not yet seen a
Reflecting Telescope of 7 Inches Aperture
which did not define Stars much better when
it was contracted in a certain degree.

That excellent Optician, and candid wri-
ter, Mr. Peter Dollond, observes of his Achro-
matics, that " though the surfaces of the Con-
cave Lens, may be so proportioned as to
aberrate exactly equal to the Convex Lens,
near the axis, yet as the refractions of the
two lenses are not equal, the equality of the
aberrations cannot be carried to any great
distance from the axis." See Mr. Dollond's
Letter to Mr. Short in the Phil. Trans, for
1765.

I had an Achromatic of 3 r yhs Aperture,
which was a remarkably brilliant Day Tele-
scope, and with which I saw Planets very
well — but could not see Rigd and several
other delicate objects distinctly, until its Ob :
ject Glass was limited to 2f inches — with
3_6_ths — the small Star accompanying Rigel
was enveloped in the false light from the
large one— with 3 T 3 ^ths inches — it was not

DOUBLE STARS.

143

much better — but with 2| inches, the little
Star was verjr distinctly, and easily visible,
— and it exhibited, s Bob'tis — y Leonis, &c,
better than I have generally seen them with
Telescopes of 2f inches Aperture.

Those who have Telescopes which do not
define Stars so well as they wish — may, sup-
posing the aperture to be 2 T 7 F ths, make a
pasteboard cover for the Object end, with an
aperture of 2-A rhs — and if that be too large,
contract it to 2 T 5 ^ths, and so on by lOths till
the Image of a Star is neatly defined.

The best Advice I can give to Buyers of
Telescopes, is, that — if they are particular
about the Quality of the Instrument, the less
curious they are about the Price, the more
likely they are to be pleased with the per-
formance of it — if they deal with an Optician
of established character, and leave it to his
Judgment and Integrity to choose for them — •
not restraining him in Price — my own expe-
rience assures them, they have then, the best
chance of obtaining what they desire.

For instance, a common portable Two feet
Achromatic Telescope which is made mere-
ly for Day purposes and magnifies about 30
times, is sold for £4, 4s. ; — if this is required
to carry a power of 100, i e. three times the
power it was made to bear ; and to define

144 PANCRATIC EYE-TUBE*

Double Stars, &c. — it must have a picked
Object-glass, — of a degree of perfection,
which is only attainable by a casual concur-
rence of the various circumstances which
combine to form these Compound Object-
glasses.

The Planet Jupiter was till within the last
30 years considered the grand test of Tele-
scopes for Celestial purposes, — and when it is
near to the Meridian it is a pretty severe one —
but many Glasses will define a Printed Pa-
per, and shew the Planets very well, which
will not so well define Double Stars, because
they were not adjusted at a Star.— Double
Stars were not thought of till the attention of
Astronomers was called to them by Sir Wil-
liam Herschel publishing his Catalogues in the
Phil. Trans, for 1782 and 1785 — since that
time, the Art of making Telescopes has been
gradually improving, and both the Optical
and Mechanical parts of them are now made
much more perfect than they were Twenty
years ago.

For exquisite perfection, — we are, in all
mechanical matters, almost as much indebt-
ed to accident, as to Art : — for instance, -a
Watch-maker makes a Dozen Chronometers,
and bestows an equal degree of attention to
the finishing of each of them ; so much so ?

DOUBLE STARS. 145

that he has reason to hope they will all per-
form equally well : however, — when put to
the trial, he commonly finds, that of the
Dozen, — perhaps Four, in spite of all his care
and pains, will turn out but indifferent Watch-
es, — Six of them good,— and the remaining
Two, fine, and fit to

"Correct Old Time, and regulate the Sun."

But why Two of his Watches perform with
such superior accuracy beyond the others he
cannot imagine.

In every department of Art it is the same,
the Acme of Perfection is always accidental, —
and the most experienced and pains-taking
workman cannot attain it with undeviating
certainty by any Rules — this Observation
applies to a Telescope even more than it does
to a Watch — for the Optician has not only to
contend with the difficulty of workmanship
— but with the greater uncertainty of the
quality of the Material he employs ; and if
not One in Half a Dozen Chronometers will
measure Time truly — not one in a Dozen
Telescopes which perform perfectly well for
all other purposes, will define Double Stars
sharply— and accordingly, those which will,
bear a proportionately High Price.

Very few persons, however, require Tele-
scopes for this purpose, Objects which are
13

146 HOW TO ADJUST

so severe a test of a Telescope — -are as se-
vere a trial to the Sight— and those who have
due regard for their Eyes, forbear from
straining them by all needless exertions.

See the account of an alarming Dimness of
Sight, from such fatigue of the Eye, in pages
59 and 60 of this work.

CHAPTER XVIII.

OPERA GLASSES.

" Ne damnent, quse non intelligunt."

This entertaining Optical Instrument, seems
to have escaped the observation of preceding
writers on Optics — the whole, of the " Lex
Scripta" which I have seen about it, is, that
" An Opera Glass" is like a Galilean Tele-
scope, and composed of a concave Eye-glass
and a plano-convex Object-glass — and that
its Magnifying power will be augmented, in
the proportion, that the focal length of the
former is diminished, and that of the latter is
increased.

As so little has been written on this sub-
ject — I have embraced this opportunity of
endeavouring to communicate such informa-
tion's I have collected concerning it.

OPERA GLASSES. 147

Few Persons know even

" How to Adjust an Opera Glass — "
partly from the want of this knowlege, and
partly from the very low Magnifying power,
and imperfect construction of Common Opera
Glasses — I have not been much surprised,
when I have heard people insist, that such
Instruments are useless Machines, — which
are made merely to be sold. Others, from
not knowing how to adjust them, I have heard
complain that their Ej'es are always so much
strained by looking through them— that they
are afraid to use one.

To look through a Good Opera-Glass, when
it is properly adjusted, — I have not found to
be more fatiguing to my own Eye, — than to
look with as earnest attention- — at the same
Object, — for the same length of time, with
my naked Eye. These mistakes of Ignorance
and Impatience, would not happen so often,
if the Instruments were properly construct-
ed, and if, in the Case of every Opera Glass,
there were pasted Plain Directions for ad-
justing it to Distinct Vision.

The irritable state of the Eyes, which some
Persons complain of, after having passed the
evening at a Theatre, is not a mere local af-
fection, — but is to be attributed chiefly, to
that general exhaustion of their nervous En-

148 HOW TO ADJUST .

ergy, which many suffer when they do net
retire to rest at their accustomed hour. — Sec
pages 58, 59, and 60 of this Volume.

To give some idea of the Focus, Opticians
sometimes draw a line round the Tube,*
where it is most distinct for a Common Eye
at the distance commonly required in our
Large Theatres, which, to see the Scenery in
perfection, is seldom less than about 50 or 60
feet.

When You use an Opera Glass,-— -hold the
Outer tube in one hand, and the Inner with
the other hand — and while looking through
the Glass at the Object you wish it to shezv you,
adjust it patiently and precisely: — thus, —
press the Eye tube towards the Object Glass,
Vision will gradually increase in distinctness
as the Eye glass approaches its proper dis-
tance from the Object glass, and when there,
the Object will be seen perfectly and sharp-
ly denned — if the Eye tube be put in be-
yond the proper distance, — the object will
again become indistinct, and in that case,

* As the Reader may have observed, that the Spying
Glasses which are in use at Watering Places — and at Sea -
— have a mark on their tube which is called the place to set
it to — very few persons have any idea that every variation
in the distance of the Object, or the Age of the person,
requires a variation of the adjustment of the Glass*

OPERA GLASSES. 149

the Eye tube must be withdrawn again : — a
very little practice, will enable a person
easily to obtain the precise point at which
the most perfect distinctness can be obtain-
ed. — This is a much better way of adjusting
an Opera Glass — than to put it up to the
Eye, and then pull out the Inner tube — by
which act, if the tube does not slide regular-
ly, or is shorter than you expect, it may
suddenly slip out, and strike your Eye. To
prevent this — in the best ^finished Opera
Glasses the end of the inner tube is attach-
ed to the outer tube by a spring which
screws in.

The greater the Magnifying power of an
Opera Glass, the greater nicety is required
in adjusting it.

If You wish tG see any thing 1 or 20 feet
further off, or as much nearer^ — for each va-
riation of distance, a corresponding varia-
tion of Adjustment is required ; i. e. of the
distance of the Ocular Glass from the Ob-
ject Glass — which must be diminished, in
the proportion that the distance of the Ob-
ject is increased. This caution is quite ne-
cessary — I have met with many persons
who have condemned an Opera Glass — be-
cause they could only see some objects dis-
tinctly with it, and for others they found it
13*

160 HOW TO ADJUST

useless— merely, because they had not been
told, that — every variation of the Distance of
the Object, requires a corresponding variation in
the Adjustment. More Opera Glasses have
been condemned for the want of this know-
ledge than from any other cause— and more
Eye and Object Glasses have been spoiled.
Those who are not aware of it — suppose,
that when they turn their Opera Glass to an
Object to which it is not adjusted — its
Glasses want wiping, arid they keep rub-
bing, till in a little time they render them
about as unfit to look through as Ground
Glass.

To See an Object distinctly at any given
distance, The longer and older the Sight of the
Person, the longer the tube must be drawn
out— Thus — if a person of 20 years of Age,
who has a common Eye, has adjusted an Ope-
ra Glass with a power of 4, for distinct
vision at the distance of 60 feet — and wishes
to set it so that a person of 40 or 50 years
of Age, who uses Convex Spectacles of 36
or 30 Inches focus, may see as distinctly 1
with it an object at the distance of 60 feet-
he must pull out the tube about the eighth-
of an Inch further, — more or less, as the
Eye is longer or older, and the Magnifying
power, and the distance of the Object, are

OPERA GLASSES. 151

more or less, — or they must look through
the Opera Glass with their Spectacles on.

Near-sighted People, when they wear their
Spectacles, See at the same focus as persons
who have a common eye — without their
Spectacles the tube must be pushed in near-
er to the Object Glass.

If an Opera Glass has been kept in a Cold
place, it very commonly happens that soon
after a person has taken it from its case, a
Mist will spread itself over the Glasses, so
as to prevent his distinguishing any Ob*
ject. — This, arises from the cold air within
the Tubes, becoming condensed on the
Glasses, either by the heat of the hand or
of the house, — if the Inner tube is drawn
out from the Outer tube, the Mist will pre-
sently go off, and the Glasses become quite
clear — without any wiping.

The best way of holding an Opera Glass,

If you put it up to your Ri^ht Eye, hold
it with your Left Hand — in such a manner, :
that the Left Arm forms a blind before the
Left Eye.

Some Fidgetty folks, when not looking
through their Opera Glass, keep ever and
anon, pawing, and wiping the Eye or the Ob-
ject Glass ; — neither of these should be
touched, — except when it is absolutely ne»

152 OPERA GLASSES.

cessary to clean them, and then, only with a
bit of soft Leather, fine Linen, or the finest
Silver Paper.

The Sliding Tube soon becomes dirtied by
the dampness of the hands ; — to avoid this,
do not touch the Sliding Tube, but take hold
only of the Neck of the Eye-head, and ad-
just by that. The Sliding tube must be wiped
occasionally, and at the same time wipe round
the cloth lining of the larger tube — so that it
may slide smoothly — if it will move only by
fits and starts, you will not be able to adjust
it accurately.

I have heard persons (unacquainted with
the Laws of Optics,) complain, that an Opera
Glass magnifying 4 times, has not so large a
Field of View as a Glass which magnifies
only 2 — this cannot be remedied; — their
only alternative, is to have a small Field
distinct, or a large Field of little or no use —
with a power of 4 they have in quality, what
with 2 they have in quantity, — the objects
which they do see, they see much more
than twice as distinctly.

In 1801 there sprang up " the Grand Dandy
Opera Glass" with a Great Eye glass, as big,
as its Object glass! — it was imagined, — by
the Amateur Optician who introduced it,—
that by increasing the diameter of the Eye-

OPERA GLASSES. 153

glass, the field of view was proportionately
increased,— and that the Stops* which had
heretofore been placed as Sentinels to pre-
vent the intrusion of false light, — were im-
pertinent impediments.

The fact is, — these great Grand Dandy
Eye-glasses, actually magnified very little,
and on that account had a very large Field
-—hold a Card with an aperture of half an
inch in diameter, before the large Eye-
glass — you will find the field of View as
large, and the Vision as bright through that,
as through the Eye-glass of an inch and a
half in diameter :~- or, apply a Concave of
an inch and a half in diameter, which makes

* These are often opened too Large, especially in Ope-
ra Glasses made with a Single Object Glass. — As the Eye-
glass should be a little Larger — so the Stop should be a
little {very little) not more than one-twentieth of an Inch
less, than the cone of Rays coming from the Object-glass.

The effect of the Stop varies according to its distance
from the Object-glass.

The Diameter of the Aperture of the Stop, must be pro-
portioned to the Degree of the Magnifying Power — the
former must be contracted, in proportion that the latter is
increased — if it is too large the Vision will be confused and
indistinct by the intrusion of False Light, if it is too small
part of the pencil of rays will be cut off.

The subject of Stops is excellently illuminated in a
Paper on " Indistinctness of Vision, "' , caused by the pre-
sence of False Light in Optical Instruments ; and on its
Remedies, by C. R. Gorijvg, M.D., in the Journal of
Science, No. xxxiii. for April 1824.

154 OPERA GLASSES.

them magnify 4 times, and you will find that
the field of view is not a hair's-breadth wider
through that than it is through an Eye-glass
of only half an Inch in diameter.

Vision through the Smaller, is more distinct
than through the Larger Eye-glass : — the
Eye is apt to wander about before large Eye-
glasses, and the margin of the field of view
is curved, — Vision is perfectly distinct, —only,
when you look precisely through the centre of the
Eye-glass.

I shall relate some further Observations,
PRO and con Concave * Eye-glasses — when I
treat on the comparative Illuminating Pow-
ers of Cassegranian, Gregorian, Newtonian,
and Achromatic Telescopes in the Second
Part of this Work.

The field of view in Telescopes construct-
ed with Convex Eye-glasses, — is regulated, by
the Stop which is placed in the focus of the
1st Eye-glass, or that next to the Eye; —
the diameter of the Stop is regulated by the
diameter of the 2d Eye-glass, the diameter
of which, varies according to the Magnify-
ing power used. If the Stop be opened

* See several Remarks on Concaves in Sir W. Hers-
chel's paper on the Quintuple Belt of the planet Saturn.—
Phil. Trans, for 1794, vol, lxxxiv. p. 28; and in vol*
ev. p. 296,

OPERA GLASSES. 155

larger than the 2d E. G. it will produce a
strong Orange Colour around a very indis-
tinct margin — with the same Magnifying power,
the field of view is the same, whether the
Aperture of the Telescope be One inch, or
Three. This is easily proved, by contract-
ing the Aperture of a Three Inch Telescope
to One Inch, when the field of view will re-
main the same ; — you will find that the only
difference in its appearance, is the diminu-
tion of the brightness of it.

But with Perspectives or Galilean Teles-
copes, or Opera Glasses which have a Con-
cave Eye-glass — -77ie Field of View, when they
do not magnify more than Twice, depends in a
great measure on the Diameter of the Object
Glass.

If an Object Glass of an Inch and a half
in diameter, is made to magnify only twice,
it will have a much larger field than an
Object Glass of an Inch in diameter.

But when a Magnifying power of 4 times
is applied, — an Object Glass of an Inch aper-
ture will have very nearly as large a field as
one of an Inch and a half — but through the
larger aperture, Objects will appear twice as
bright, as they do through the smaller, the
Illuminating power of the larger, to the small-
er aperture, being as 22 to 10. — These facts

156 OPERA GLASSES.

any body may prove, by looking through an
aperture of an Inch and a half, and then con-
tracting it to an Inch.

Some of our most valuable discoveries
have been purely accidental. — as little the
result of scientific investigation, as the Tele-
scope, which was found out by Children play-
ing with the lenses in a Spectacle-maker's
workshop : — these Great Grand Dandy Eye-
glasses, as big as Object Glasses, led me to
consider — what Diameter of Eye-glass and
Object Glass is actually useful.

Theoretical Opticians, — have said, — that
if the Eye-glass, be as large as the Pupil of
the Eye-^-it will perform as well, as if it was
as big as the Dome of St. Paul's.

The Opening of the Pupil of the Eye is in
inverse proportion to the Brightness of the
Objects presented to it — as the latter in-
crease in Brightness, the former diminishes
in Diameter, therefore — the less the magni-
fying power, the less the Pupil of the Eye —
which is always in an inverse proportion to
the bigness and brightness of the pencil of
Rays from a Telescope.

The ordinary opening of the Pupil, when the
Eye is turned to the Light, has been com-
puted to very little exceed ~gth of an Inch
in Diameter ; See Figure 3 in the Engraving,

OPERA GLASSES, 157

fronting the Title, and No. 10 of the Appen-
dix.

Under the idea, that the opening of the
Pupil when before an Opera Glass, is of the
like dimension, it has been assume d, that — no
matter what be the Magnifying power, or
what the Diameter of the Object Glass of an
Opera Glass, an Eye-glass of T 2 oths of an Inch
in Diameter, would be even larger than is re-
quisite.

My Eye, had for some time suspected the
Truth of this Theory : — wishing to avail my-
self of the amusement of a change of Mag-
nifying power, and to have an opportunity of
illustrating its effects to others, I had a Re-
volving Eye head made like the double Head
of the French Opera Glasses, invented by
Mr. Cauchoix,* with two Glasses — one mag-

* I have had thi'ee very good Achromatic Opera Glasses
made for me by this Optician, of an Inch and a half, — and
One of Two Inches aperture ; but the latter size is heavy,
and inconveniently, and I think, uselessly large, — its Dou-
ble Object Glass weighs 5 ounces, and the Instrument alto-
gether 9 ounces, and cost 51. in Paris. — See an account of
Mr. CaUCHOIx's Opera Glasses, in page 374 of the Edin-
burgh Review, for October, 1819.

Mem. I do not quote this, because I am of the same
opinion as the erudite Editor of the paper referred to — my
own opinion of Opera Glasses, is impartially stated, at the
termination of this note.

Lemiere, No. 6 Palais Royal, has introduced an
Opera Glass with a Screw adjustment, similar to what our
14

158 OPERA GLASSES.

nifying 3, the other 4| ; the Eye-glasses were
T \ths of an Inch in diameter — and I was sur-
prised to find, that on trying an Eye-glass of
half an Inch in diameter, Vision was consi-
derably brighter and easier to my Eye.

The Magnifying Power of an Opera Glass,
may be varied several different ways :

1st, By having a Concave fixed in the
Eye-head which magnifies 2J, ?fbr viewing
Pictures, &c. — and another to screw on over
that, which will increase the power to 4, for
Theatrical purposes ;

One foot Achromatic Telescopes in a Brass Tube on a
Stand have — but the adjustment is so fine, that it is more
difficult to find the exact focus with it — than it is bj' moving
the Tube, provided that be kept clean and slides smoothly :
his charge for an Obera Glass with this adjustment and an
Achromatic Object Glass of an Inch and a half in diame-
ter, magnifying 2 1-2, is 21. 4s.

The machinery for adjusting the focus, may be as much
too fine — as too coarse — The fine Screw adjustment, which
stills seems the best that can be applied to Gregorian Re-
flectors, was applied to the original 46 Inch Achromatics —
but when even a power of 150 is applied to them — it is not
quick enough, and the focal point is not half so easily and
exactly hit, as with the more modern invention of the Tooth
and Pinion adjustment on the side of the Tube.

I do not mean to insinuate, that I think the productions
of our English Opticians are not equal to those of the Pa-
risian Artists — I have had several Dozens of Opera Glasses,
made by Mr. Pierce and Mr. Dollond, which are as
elegantly formed and finished — and the Optical parts, are
as perfect as Art can produce : — For, a Description thereof,
tee, pp. 153, 154, 156, &c.

OPERA GLASSES. 159

2dly, By having a Concave fixed in the
Eyehead which magnifies 4 — and a Convex
to screw on over that, which will reduce the
power to 2j-. I like this last plan best, be-
cause most light is required for theatrical
purposes. The additional Glass may be at-
tached to the Eyehead by a hinge on the
side ; and when only one of them is wanted,
the other may be turned up. The opening
of the Stop in the Eyehead must be regulat-
ed to suit the deepest power: — or when that
is used, a smaller Stop must be brought be-
fore the larger one, in the manner in which
the Sun Glass is brought before the Eye
Glasses in the 4 Eye Glass Perspectives.

I am induced to offer it as an invariable
maxim, — that although there may be no use
in the Diameter of the Eye-glass being much
larger, yet, it should be somewhat larger than
the Pencil of Rays transmitted by the Object-
glass — which, when an Object-glass of 1J
Inch Diameter magnifies 3 times, will, if not
cut off by the Stop,* be \ an Inch. (See next
page.)

* To ascertain whether any of the Object-Glass is cut off
by the Stop in the Eye-tube— -adjust the Opera Glass to
distinct Vision — then, take out the Eye-glass, put your
Finger on the edge of the outside of the Qhject-glass, and.
look down the tube — if you can see your Finger just peep=»
brig over the edge of the Object-glass— none is cut off 9

160 OPERA GLASSES.

As I have before observed, it has been as-
sumed that the opening of the pupil of the
Eye, when before an Opera Glass, is about
T Vth of an inch in diameter ; — 1 believe it
does not exceed r a oths, — that the Image is
brighter with a pencil of three tenths and
three quarters than it is with one of three-
tenths, my Eye assures me is evidently true
—but why the larger pencil of rays makes a
stronger impression on the Eye, I will not
pretend to offer any reason* — I know, it is
contrary to the accepted Theory — however,
it is True.

" There are more things in Heaven and Earth, Horatio,
Than are dreamt of in your Philosophy."

Shakespeare.

The Diameter of the Eye-glass , for any
Opera Glass, and any Magnifying power —
should be rather more than what is given,
by reducing' the diameier of the Object-
glass into Tenths of Inches, and dividing
that, by the Magnifying power —

Thus : for an Object-glass of 1 Inch and
a half, — or fifteen lOths in Diameter, — if a
Magnifying power of 4 times be desired, di-
vide 15, — the number of Tenths the Object-

* See Sir Wm. HerscheVs observations on Night classes.
in page 68 or 69 of Vol. 90. of the Phil. Trans.

OPERA GLASSES. 161

glass is in diameter— by 4, the Magnifying
power : —

4)15( T 3 ^ths and fths, the diameter of the
12 Pencil of Rays.

I would have the Eye-glass somewhat larger
than the Pencil of Rays, i. e. for an Object-
glass of ]| inch in diameter, and magnifying
4 times, I think that my Eye sees easiest,
when the opening of the Aperture in the Eye-
head is about fths of an Inch in diameter.

The Eyehead should be of Black Ivory,
not less than an inch and -Jths in diameter,
and made concave — something in the form of
an Eye-bath — or a shade on the side similar to
those prefixed to the Tubes used for viewing
Pictures — so that it may form a Screen
around the Eye, and prevent the intrusion of
any rays upon the retina, except those coming
directly from the Opera Glass- — this, will not
only improve the Vision very much, but also
render it much easier to the Eye. (See page
78 of this Vol.)

The average Distance, at which a Common
Eye, can see distinctly, the expression of the
Human Countenance (in a good light) has
been calculated to be about 15 feet.

The average Distance, between the Actor and
14*

162 OPERA GLASSES.

the Spectator, in the Boxes of a Theatre, is
about 4 times 15 feet, i. e. about 60 feet —
therefore, — to shew distinctly, — an Opera
Glass must magnify 4 times.

The Bell Operas, which have -only one
sliding tube, are the best ; in those which
have more tubes, the centre of the Object-
glass and the centre of the Eye-glass are
very seldom exactly opposite to each other
—and in proportion as they are Eccentric,
Vision is Imperfect, and the Instrument (ac-
cording to a very usual and very useful Op-
tical phrase) is said, to be Out of Adjust-
ment.

Look with a scrutinizing Eye through
Operas zvhich are elaborately ornamented and
have many Tubes — for it is one of those
General Rules which has the fewest excep-
tions, that those which are so very pretty to
look at, are— not seldom— mere Toys, which
are made to be looked at, rather than to be
looked through.

This Caution is quite needful, friendly
Reader — for I think I have been as much
puzzled to produce arguments to persuade
my friends that Opera Glasses are not always
to be chosen for their Tubes, as I have had
to assure them that — a Piano-Forte will not
always make good its claims, to favour from

OPERA GLASSES. 163

the Ear— exactly in the proportion that its
external appearance happens to please the
Eye.

As Ten are made of the plain mountings,
to One of* the other, it is, in like proportion,
easy to pick out a fine one.

The majority of the Opera Glasses which
are sold at Trinket and Toy-shops, magnify
so little, and are of so little use — that many
people who have good Eyes, say with truth,
that they can see as well with their naked
Eye— I have met with many who have said
so to me — but, when I have shewed them a
good Opera Glass, magnifying 4 times, precisely
tuned to the peculiar pitch of their Visual Organ
. — they have All, acknowleged, with astonish-
ment and delight, the surprising aid that their
Sight received from the Eye-invigorating
power of Optics, which enabled them — to
See Persons in the most distant parts of the Thea-
tre, almost as distinctly, as those zvho were zvithin
15 feet.

After a deliberate, and fair trial of the
Magnifying powers of 3 — 4 — 5 — 6, &ic, my
Verdict is, — that for use in the Theatre, for
Common Eyes, a Magnifying power of about
4 times, is decidedly, the most generally useful
and agreeable, — and what is of great impor-
tance, as the Eye is sometimes before it for

184 OPERA GLASSES.

a long time, it is— much easier to the Eye than a
Higher Power.

Persons who are extremely Short-sighted, —
(See the Note at the foot of page 93), may
find a Concave which produces a power of
5 to a common Eye, not too much for them.

It is desirable, that the Magnifying Power
be as Low as can be, that the Field of View
may be as Large as can be ; because the lat-
ter depends party on the former — moreover,
the vapour from the breath of a large As-
sembly, and the Smoke from the numerous
Lamps, &c. prevent our using much Magni-
fying power.

When I suggested my opinion of what ought
to be the Magnifying power of an Opera Glass
to an Optician — I was told, "It has been
tried — but the less they magnify, the more
people like them ; and indeed, those seem to
me to be most approved, which magnify so
little that they scarcely require any Adjust-
ment."

Exquisite Opera Glasses, that have no focus!
— and are equally distinct, whether all the
Eye-tube is pulled out, or all put in ! ! — or
you put up the Large, or the Small end to
your Eye ! ! ! — My Optical friend added, with
a smile, " You may laugh, Sir, — but every
body has not time to listen to a Long Story
about— Focus j — Adjustment, &c. &c. &c. —

OPERA GLASSES. 165

Gentlefolks don't like a troublesome thing, — •
that requires Half a Minute to set it in some
particular form, before they can see through
it."

Opera Glasses have been one of my fa-
vourite hobbies for the last Thirty Years —
and to gain the information contained in these
pages, I have carried my experiments to the
greatest extent possible, for I think 1 have
tried almost All Apertures and All Focal
Lenghs — I had one Object-glass made by
Mr. Pierce, of 4 Inches in Diameter— and
from that Brobdignagian, he made for me all
the intermediate sizes, down to the Lillipu-
tian, which I have called my, " Invisible Ope-
ra Glass" whose Object-glass is only T 6 pths
of an inch in Diameter, and of which an ac-
count is given in page 93.

My favourite Single Object-glass Opera Glass,
which is very portable, and very light, for
it only weighs two Ounces, — has a Piano
Convex Object-^lass, of one inch and T yhs
in Diameter, and usually magnifies 24, but
with a deeper Eye-glass of 1 \ths for Com-
mon Eyes, or l T 3 o-ths for the extremely short-
sighted, Mr. Doilond informed me, may be
made to magnify about 4 times, and is in his
Catalogue called the Middle Size Opera
Glass, with a Nourse Skin tube, and mounted
with dyed Ivory — its price £\. 1

166 OPERA GLASSES.

The most effective Achromatic Opera-glass for
general use, which I have seen, is Mr. Dol-
lond's Bell Opera of an Inch and a Half aper-
ture, with a Power of 4— it is conveniently
portable, an entertaining companion at a Play-
house, and a very pleasant Prospect-glass.

If the Eye-glass is changed, for One which
makes it magnify Twice, it will be an excel-
lent Instrument to assist the Sight to view
distant Pictures at Exhibitions, $-c, which it
will shew with very beautiful effect — and
Short-sighted persons (especially) will find it
an incomparable assistant to give them a
General View of the Constellations, — and it also
deserves to be recommended as an excellent
Finder to such as are fond of turning out on
a fine frosty night to sweep the sky for a
Comet, — those who are not, or have not
Courage or Constitution to brave the incle-
mency of mid-night Frosts and Damps, with*
out which, actual Astronomical Observations
cannot be made, I recommend to pay a visit
to the

OURANOLOGTA,*

* This Lecture on Astronomy and the Phenomena of the
Heavens and of the Earth, is annually given during Lent,
at the English Opera House, on a Magnificent Orrery, de-
scribing a circle of One Hundred and Thirty Feet. In this
immense Machine, the Sun, and all the Planets and Sa-

OPERA GLASSES* 167

in which is shewn the most beautiful and
perfect Orrery ever exhibited, and is one of
the most Instructive Exhibitions that youth
can be taken to.

" Stars teach as well as shine."

" An Undevout Astronomer is mad."

" The Heavens are telling the Glory of God, and the
Firmament sheweth his handy work."

<{ These are Thy Glorious Works,
Parent of Good, Almighty."

tl A Deity believ'd, is Joy begun ;
A Deity ador'd, is Joy advanc'd ;
A Deity belov'd, is Joy matur'd."

Dr. Youitg.

The late Astronomer Royal, Dr. Maske-
lyne, who was shortsighted, had a Binocular
Opera Glass, i. e. two Opera Glasses, magni-
fying about twice, fixed in the opening of a
Spectacle frame, which he placed before his
Eyes, like as you put on Spectacles. I re-
member seeing a pair of such Spectacles in

tellites revolving round him, are seen in motion, with their
comparative Diameters and Orbits. The Comet of 1811,
descending in its eccentric orbit towards the Sun, arriving
at its perihelion, and retrograding, being an original and
entirely novel mode of exhibiting and illustrating this beau-
tiful Phenomenon.

Mr. Bartley well deserves the fame he has acquired,
by the impressive manner in which he delivers his illustra-
tions of these sublime subjects, which are expressed in
terms perfectly intelligible, and spoken so distinctly, as to
be perfectly audible in the most distant parts of the Theatre,

168 OPERA GLASSES.

the Observatories, of Mr. Larkins, on Black-
heath Point ; of Mr. Aubert, at Highbury :
and of Mr. Hodgson — at Hoddesdon.

For those purposes which do not require a
Magnifying power exceeding 2£ — a Singh Ob-
ject Glass of 5h inches focus, and of l T Vhs in
diameter, is, very nearly, quite as good as an
Achromatic, and costs only half as much.

The Colorific, and Spherical Aberrations,
which cause that fringe of colour, and indis-
tinctness around the margin of the field of
view of Single Object-glasses — which arise
in an extreme degree, when the Aperture of
a Single Object-glass, is too large, for its fo-
cal length — or the Eye-glass is too short and
magnifies too much — and are sometimes so
glaring when such a Glass is pointed at a
highly illuminated object in the Day time —
are often hardly, if at all, perceptible in a
Theatre, unless it be directed to the Lights.
But half the errors of aberration arising from
the over large apertures of Single Object
Glasses are rendered imperceptible in most
Opera Glasses — either by a small Stop cut-
ting off half of the cone of rays, or the Eye
Glass, or aperture in the Eyehead, not being
half large enough to receive them — and while
the observer imagines that his Object is illu-
minated by an aperture of II inches, perhaps

OPERA GLASSES. 169

he has, in fact, not the use of an aperture
of li.

Concave Eye-glasses may be had for \s. 6s,
each — and it will afford some amusement to
have three or four — Magnifying 2 and 3
times, for viewing Pictures — 4 for the Theatre
—and 5 or 6 as a Perspective Glass, for use at
a Review, or on a Race-course, &c. For
15s. every degree of Concave may be pur-
chased — that is from Two inches to One inch
focus — proceeding by tenths of inches : thus
— any one who is anxious to give his Eye all
the assistance that Art can afford it, may
readily do so to the utmost nicety.

The following Rules will serve for ascertain-
ing the comparative degrees of the Magnifying
Power of several Eye Glasses, although, gen-
tle Reader, you may think that the 1st — is
one of the completest Paradoxes you ever
met with.

1st. " The more a Glass Magnifies, the more
it Diminishes ;" — i. e. if you have two Con-
caves, or Convexes, and wish to know which
magnifies most — hold one in each hand,
about one foot from your Eye, and about five
feet from a window frame — the Lens through
which the panes of Glass appear least, — mag-
nifies most; — this is the readiest wav of
15

170

OPERA GLASSES.

ascertaining the comparative power of various
Lenses.

2d. The further the Eye-glass requires to
be removed from the Object-glass, and the
more the Inner tube must be drawn out — -the
more the Eye-glass magnifies. If an Opera
Glass magnifies 3, and the Eye-glass is chang-
ed for a concave which is a little deeper to
make it magnify 4 times, to obtain distinct
vision the tube will require to be drawn out
further.

The Double Object-glass before-mentioned
is an Inch and a Half in Diameter ; its
length, when in use, when it magnifies 4
times, is about 4 Inches ; and with its tubes
weighs 3 and I Ounces ;- — a larger Glass is
cumbersome to carry, — an unsightly machine
to use;- — and the additional Illuminating and
Magnifying power gained by a larger aper-
ture and longer focus — are in a Theatre, of
very little, indeed 1 think of no use.

There is no need of a Magnifying power
of more than 4 times — nor of a pencil of rays
of more than three tenths and three quarters
in diameter, which is given by an Object-glass
of an Inch and a Half in diameter.

That the Field of View is considerably
larger through an Object-glass of Two inches
in diameter, if the Magnifying power be as
much as 4 times, is a Vulgar Error,

OPERA GLASSES. 171

The increase of the field of view in the
larger Object-glasses is comparatively very
trifling, and much more than counterbalanced
by their unwieldly weight and length. — More-
over, the difficulty of making Object-glasses,
as their diameter is increased, increases in sq
high a ratio, that those of Two inches, very
rarely define Objects so perfectly and sharply,
as those of an Inch and a Half in diameter.

In every department of Art, the acme of
perfection is always partly accidental, and is
not to be attained with undeviating certainty
by any Rules; and as there are 100 of 1£
made for 1 of 2 inches aperture — it is in the
like proportion, more easy to select a Fine
One.

Imperfections in the Object-glasses of Opera
Glasses, like those of Telescopes, are magni-
fied and become evident, as the Magnifying
power of the Eye-glass is increased.

Defects in an Object-glass which, when it
magnifies only Twice, are almost impercepti-
ble — when it Magnifies Four or Five times,
become too glaring; to pass muster before a
good Eye — the Vision, (especially the mar-
gin of the field of view,) becoming less Sharp,
and the edges of the Objects being fringed
with Colour.

Opticians charge £2. 12s. 6d. for the Best

172 OPERA GLASSES.

Achromatic Opera, in a plain mounting, with
an Object-glass of H inch in diameter and
which magnifies 4 times — £2. 25. for the
Common Achromatics, which magnify 2i —
and £1. Is. for those of like power with Sin-
gle Object-glasses.

I must here caution my Reader, that the
real, or the relative powers, of various Opera
Glasses, can only, be accurately appreciated by
actual trial in the Theatre, in which they are
to be used — especially, companions of Ach«
romatic and Single Object-glasses ; and unless
particular care be taken that they are glass-
ed with precisely the same kind of Glass — -
with Concaves which give precisely the same
Magnifying power — and the Glasses are di-
rected to the same Object, at, as nearly as
can be, the same time ; and the Ocular Glass-
es and Object-glasses are all perfectly clean
— Comparison will be in vain.

The difference of even Si and 4 in the
degree of Magnifying, will, with some objects,
give quite a different character to an Opera
Glass, — even if the Object-glasses and Eye*
glasses are equally good.

An inexperienced person, will say that
the Opera Glass which magnifies 4 times,
defines some objects more distinctly than that
which magnifies only 3£— but that there is a

OPERA GLASSES. 173

greater degree of brightness about the latter,
and that the vision in it appears clearer : —
This, is thus to be accounted for, — the lower
the Power, the clearer and brighter objects
appear — and up to a certain maximum, (which
I think for use in a Theatre is about 4 times,)
the higher the Power the better minute objects
will be defined, and the sharper and more
distinct the Vision will appear.

The Achromatic Object-glass above-men-
tioned, is composed of a Piano Concave lens,
and a double Convex* which, combined, are
generally (in every part) of the thickness of
about -fths of an Inch.

The thickness of the usual Piano Convex
Single Object-glass of the like focus, — in the
central and thickest part of it is seldom more
than fths of an Inch, and in the thinner parts,
not half that : — however, such is the advan-
tage of the Achromatic — that if you compare
« Single, and a Double Object-glass of li

* Sometimes a Film or Fog forms between the Object-
glasses, or, as the Optical phrase is, " the Glasses sweat :"
— when this happens, they must be taken out of their cell
and wiped with a bit of soft Leather or of very fine Silver
Paper — but never do this but when it is absolutely needful
— and then, take care to replace them in the same position ;
it is seldom requisite oftener than once or twice in a Year.
Nor wipe the Object or Eye glass except they really require
it — as often as you wipe them — you scratch them a little.
15*

174 OPERA GLASSES.

inches in Diameter and 4i inches focus, and
put to them Eye-glasses which make them
magnify 4 times, you will find that Vision,
(excepting just in the centre of the field of
view in the Single Object-glass.) is more
distinct, and objects are more sharply defined
through the Double, than they are with the
Single Object-glass. If you contract the
aperture of the Single Object-glass to l-^-,
you will find the Errors of Aberration consi-
derably diminished — and more so if you li-
mit it to l T V ns ? an d if the focal length of your
Single Object-glass is increased from 4i to
6 Inches, its vision will be still more im-
proved. If its aperture be 1-^ths, the open-
ing of the Stop must be limited to a little less
than T |-ths of an inch in diameter.

Tenths the Object-glass
is in Diameter.

Mag. Power 4) 12 (-^ths, Diameter of the
12 Pencil.

The Chromatic and the Spherical aberra-
tions which produce prismatic colours, and
distort the Vision in the Margin of the field
of view, — exceedingly distress the Eye, and-
which are the main Evil of Single Object-glasses
which have a larger aperture in proportion
to their focal length than an aperture of 1-^-ths

OPERA GLASSES. 175

inches, to 51 — and which magnify more than
3 times, are in a great measure corrected in
DouUe Object-glasses, with which the Image
of Objects appears more Distinct, in propor-
tion as the order in which the Rays proceed
is better preserved.

The Grand superiority of the Double or as it
is commonly called Achromatic Object-glass,
consists in the field of view being almost
quite as distinct at the margin, as it is in the
centre, and thus, Vision is made easy to the
Eye, with a considerable Magnifying power.

The Eye, is sadly puzzled, how, to adjust
itself with a Single Object-glass, /when it
magnifies more than 3 times — (especially if
its focus is less than 5h inches and its diame-
ter more than 1 i), which then becomes indis-
tinct, except just in the very centre of the
Field. I think that in the very Centre of the
field of a Single Object-glass, the vision is
quite as vivid, if not more so, than it is in a
Double Object-glass — but as only just the
very middle of the field is distinct- — looking
through it, soon becomes much more fatiguing
to the Eye than with a Double Object-glass,

Those who wish to prove this, may get a
Single Piano-Convex Object-glass for five
shillings, of exactly the same diameter and
focus as the Achromatic one I have recom-

176 OPERA ©LASSES.

mended in page 157, — and judge for them-
selves. If Vision is distinct, when the Sin-
gle Object-glass is at the same distance from
the same Eye-glass, as when the Double one
is used, the Magnifying power will be the
same — if the Eye and Object-glass must be
brought nearer together — the Magnifying
power is less, and the Single Object-glass is
of too short a focus — to have a fair compari-
son, — the focal length of each Object-glass, must
be exactly the same.

For a Single Object-glass, to be at the same
distance from the Eye-glass as a Double One
of the same focus, the Eye-glass must be
brought, apparently, full T Vhs of an Inch
nearer to the Single Object-giass — to make
up for the Double Object-glass projecting so
much further up the Tube than the Single
One does.

I formerly thought, that for use in a Thea-
tre, the Single Object-glass was best.

Until Mr. Pierce, about Five Years ago,
just before he retired from business, made me
an Achromatic Opera glass, which magnified
4 times, I had not seen a Double Object
Glass, nor do { think one had been made,-
which magnified more than 2£, which is the
power usually put to those commonly sold. —
My own excellent Single Object-glass, which

OPERA GLASSES. 1 77

Mr. P. made for me, magnified rather more
than 3i — -it is no wonder then, that I prefer-
red it to the ineffective Double ones which
only magnified 2£.

The reasons why Opera-glasses were for-
merly not made to magnify more than 2i —
were, that the small size of the Theatres at
the time these instruments were originally in-
vented, did not require more magnifying pow-
er, — and that with such a low power, the im-
perfections in vision arising from the Spheri-
cal and Colorific aberration of the Single
Object-glasses of the very large* Apertures,
with which it has been the fashion to make
them latterly, were comparatively trifling —
indeed, an Opera-glass seems hitherto, to
have been considered as apretty Tiling to Look
at — or a Play Thing to Look through —
rather, than — an useful and entertain-
ing Instrument to See with, — its Proper
Powers have never before been explained —
with such Low powers, they were easy to
Opticians to make, and to their Customers
to use.

I feel no awkwardness in publishing this re-
cantation of my former Opinion respecting
Single Object Glasses — but willingly em-

* The origin of these Great Single Object Glasses of so
short a focus, was an attempt at an imitation of the exter-
nal appearance of the Achromatic Opera Glass.

178 OPERA GLASSES.

brace this welcome opportunity of acknow-
ledging my Error — to want the Candour to
do so, — would be to want the Courage to con-
fess that I am wiser To-day, than I was Yes-
terday, — remembering the excellent Advice
given by Pope in the 368th and following lines
of his Essay on Criticism.

" Positive, persisting Fops we know,

Who, if once wrong, will needs be always so;
But You, with pleasure own your Errors past,
And make each daj', a Critique on the last."

To measure the Magnifying Powers of Opera
Glasses.

Look at one object at the same time with
both Eyes,— one eye viewing the object
through the Glass — and the other without it.

You will find some difficulty at first in keep-
ing both Eyes open in this unusual way, while
looking through the Glass ; but after a few
trials you will be surprised at the great accu-
racy and ease with which the Powers can be
ascertained.

The Object to be viewed, must not be more
distant than what the naked eye can distinctly
define; and not less distant than 60 or 80 feet.
For this purpose, the best Object to be viewed,-
is perhaps the front of a building of regular
stone work, with indented horizontal joints:
or when such an object does not readily oc-

OPERA GLASSES. 179

cur, a building of good regular brickwork will
in general be found to answer tolerably well :
other objects, as the squares of glass in a long
window, which are usually of the same size,
will be found convenient for the small powers
that are usually applied to Opera-glasses.

It will be obvious, from what has been said,
that the object to be viewed must consist of
a number of equal divisions in the height.
These divisions must be regarded by one eye
through the Opera-glass at the side and close
against the object as seen by the other eye ;
and the number of divisions seen by the nak-
ed eye in the height of one division as seen
through the Glass, is of course the Magnify-
ing Power.

The foregoing process gives the Magnify-
ing power in whole numbers. It is, however,
desirable sometimes to ascertain the power
of an i Opera-glass to the fraction of one
quarter : this may be done by marking every
fourth course of brick-work with a chalk line;
and the number of these chalked divisions
and the additional joints of brick-work seen
with the naked eye, in the space of one
chalked division as seen through the Teles-
cope, gives the Magnifying power in whole
numbers and quarters.

The Magnifying Power of any Object Glass

180 OPERA GLASSES.

of an Opera Glass, is in proportion to its dis-
tance from the Eye Glass — as I have before
observed. Therefore— a person who is so
Short-Sighted as to use a Concave No. 4, does
not derive that degree of advantage from an
Opera Glass, that a Common Eye does— the
same Opera Glass which only magnifies Si
for him, — will magnify 4 for a Common Eye,
and for a Long Sighted Eye of 60 Years old,
w r hich requires convex Spectacles to read
with, of 18 Inches focus, it may magnify 41
or perhaps rather more.

Short, and Long Sighted Eyes when they
look through an Opera Glass, with their Spec-
tacles on — will see at the same focus, and con-
sequently with the same Magnifying Power
as Common Eyes — and without Spectacles the
Near Sighted will have about, or almost, half
a degree less, — the Long Sighted, about as
much more Magnifying Power. The exact
Focal length of the Eye-glass which is best
for any peculiar Eye, will be best determined
by Experiment. See page 154.

Lastly — take care that the front edge of
the cell containing the Object-glass projects at
least the 10th of an inch beyond the surface
of the middle part of the Glass — that it may
be properly defended when laid down ; and
that it may not be soiled by the stuffing in
the top of the case coming against it ; this said

OPERA GLASSES. 181

stuffing is a mighty silly decoration, and
much better omitted — if the inside of the top
of the case be required to be double natty —
let it be lined with bright green Velvet. —
The Eye-end should be sufficiently distant
from the Eyeglass to prevent any thing touch-
ing it.

Diagonal Opera-Glasses. — To the object
end of an Opera-glass may be attached a
plane mirror, placed at an angle of 45 de-
grees, like the small speculum in a Newtoni-
an Telescope : if this be well made, and the
lateral aperture is as large as the Object-
glass, the Illuminating power is so sufficient,
that the light lost by the reflection is almost
imperceptible, and the Diagonal is almost
quite as bright as the Direct vision.

This is an entertaining Optical Plaything,
with which, you may observe distant objects,
as unobservedly, as you can those which are
near with the Circumspector, mentioned in page
75 of this work — as the Instrument points to
a different object from that which is viewed
— and as there is an aperture on the side, it
is almost impossible to guess which way you
are observing.

However trifling in value, or however im-
16

182 OPERA GLASSES.

perfectly expressed the foregoing Observa-
tions I fear are in many respects, notwith-
standing the extreme labour and care I have
bestowed in order to be accurate and intelli-
gible— I hope, that my Reader will give me
credit for having done my best, to put him
into complete possession of all the " Practi-
cal Facts" which I have been able to accu-
mulate.

Of the many " Castles in the Air," which
Theory has built at the expense of Truth, —
there are none more numerous, or less sub-
stantial, than those which have been set
up by Speculative Opticians. — I have not
aimed at amusing the Imaginations of such
Ingenious Persons with abstruse Algebraic
calculations, — or of amazing the reader with a
confounding crowd of cramp Technical terms
which are only intelligible to Practical Opti-
cians — by which, if some Writers have suc-
ceeded in exciting

"Wits and Philosophers, Scholars and Conjurers,"

to admire their amazing erudition — it has
been at the unwise expense, of rendering their
works entirely useless to the Public.

The humble efforts of the Author, have
been confined, to an ingenious Endeavour to
give a plain unvarnished account of the actu-
al results of his experience, in so clear a
manner that— All may easily and exactly
Understand.

OPERA GLASSES. 183

Truths interesting to All, should be told in
Terms intelligible to All.

Errors, and Omissions, will no doubt be
found, and from enlightened Readers, — will
meet indulgence— They ,— know,— -how un-
avoidably, — and how often, — such defects,
will escape the most persevering industry,
and most unremitted attention.

Those who are already well acquainted
with the subject, which I have devoted many
an hour to illuminate so plainly, that I hope
All may understand, may think I have upon
some matters, been tediously minute, — but if
I had not written so fully and so plainly — I
could not have enjoyed the main gratification
I receive from publishing this little book — •
the pleasure, of hoping, that it will give an
attentive Reader, in a Few Hours — what
the Writer, has been collecting Many Years.

" Content, if hence th' unleam'd their wants may view,
The learn'd reflect on what before they knew :
Careless of censure, nor too fond of fame ;
Still pleas'd to praise, yet not afraid to blame ;
Averse alike to flatter, or offend ;
Not free from faults, nor yet too vain to mend."

Pope.

CHAPTER XIX.

THEATRES.

I am informed that the distance from the

184 THEATRES.

front of the opposite Boxes to the Curtain

is —

At the English Opera House 50 Feet.

Drury Lane - - - 60 — 6 Inches
Covent Garden - - 63 — —

I am I believe correctly informed, that at
the Theatre which Garrick rebuilt in Drury
Lane, and where he established his immortal
fame, the distance from the Front Boxes to the
Curtain was not more than 47 feet 6 inches, —
and am disposed to attribute no small part of
the great admiration which 1 hear that he
excited in those who saw him act, and who
speak still of the extraordinary distinctness
with which he spoke, and of the variable and
incomparable expression of his Countenance,
— to the Spectators being so much nearer to
the Stage.

I understand from the best authority, that
at the cotemporary Theatre of Covent Gar-
den* the distance of the Spectators from the
Performers was then 8 feet further, i. e. 56
feet — and that the disadvantage of this great-
er distance, was then frequently remarked
and complained of.

" In most theatres, whoever wishes to have
a tolerable view of the Stage, must be situat-

*"In this Theatre, 1 foot 9 inches was the whole space
allowed for seat, &c. though a raodeiate-sized person can-

THEATRES. 185

ed beyond the reach of the Actor's voice —
but if he wishes to be near the Stage, he is
(in the Boxes) miserably seated sideways —
I am confident, that where the distance of 70
feet from the Scene to the opposite Boxes is
exceeded, the Actor will be heard very im-
perfectly.

" It is an universal custom to take the point
of Sight for the Scene Painting— -at the centre
of the front of the opposite boxes ; and this,
not only for the flats or end scene, but for
the side scenes also, in which it is necessary,
in many instances, to represent one continued
line, such as the side of a Room, &c. ; in which
case, the least remove from the centre breaks
this line and weakens the effect of the scene.
This demonstrates that our painted Scenes
can be viewed to a proper advantage in one
situation only ; and that they will appear de-
fective in proportion as they are viewed at a
distance from this point.

"-It has often been observed, that if we view
a person at a greater height than an Angle
of 45 degrees, the features appear distorted
and the expressions grimace.

not conveniently sit in less space than that of 1 foot 10
inches from back to front, nor comfortably in less than
2 feet." — G. Saunders, Treatise on Theatres, 4to. 1790,
p. 84.

16 *

1 86 THEATRES.

" To discern well the motions of the fea-
tures, we cannot be too near the Actor : it is
with great difficulty we comprehend them at
the distance of 75 feet, and scarcely with sa-
tisfaction at more than one-third of that dis-
tance.

" OF THE EXTENSION OF THE VOICE.

"Having traced a Circle of 100 feet in
diameter, I placed the speaker in the centre ;
the distance, therefore, was the radius of 50
feet every way — the hearer moving in the
circumference of this circle, heard most dis-
tinctly when in front of the speaker, not much
less so on each side, but scarce at all behind,
and contrary to the common notion, that
Sound ascends further than it descends —
that

" The Descension of sounds exceeds the
Ascension. "

Exp. 2.—" The Well-hole of the Staircase
in St. Paul's Cathedral, which is free of any
redundancy of sound, is about 8 feet in diam-
eter, encircled by a stone wall, and covered
with a skylight. At some distance from the"
bottom, and near the top, were alternately
placed Speaker and Hearer ; when the Voice
descending was heard at the distance of 80
feet, ascending 70 feet." — From the interest-

THEATRES. 1 87

ing Treatise on Treatres, 4to, 1 790 (published
by Taylor at the Architectural Library in
Hoi born), pages 91 , 2, 4 and 6 : this entertain-
ing Volume ^ives a Description, and the Plans
and Dimensions, of all the principal Theatres
in Europe; and in which those who desire
further information on such subjects, will find
it both minutely and plainly set forth.

I attribute Mr. Garrick's superlative suc-
cess, to his proximity to his Audience. T can-
not imagine, that there is any Part which the
English Roscius of that day played, — but that
several of our present excellent Actors per-
form quite as well.

If our Actors appear to fail in any part, it
arises from no other cause than occasionally
being obliged to overstrain their Voice,
(which cannot be done without some distor-
tion of the features.) from being at Drury
Lane 13, — and at Covent Garden 15 feet 6
inches, further from the Audience than in
Mr. Garrick's Theatre — the very superior
illumination given by the Argand lamp foot
lights, side lights, &,c. and the Brilliant Gas
light Chandeliers which are suspended from
the centre of the Ceiling, in a great measure
counteract the disadvantage of the increased
distance, as far as the Eye is concerned, espe-
cially when it is assisted by a good Opera
Glass.

.188 THEATRES.

The Magic power, which some Performers
seem to possess, of making themselves heard
distinctly all over the House, without any
apparent effort — depends infinitely more on
the faculty they have of catching and caging
the intense attention of the whole Audience
— than upon any extraordinary exertion of
their Voice.

In Mr. Arnold's Theatre, the distance
between the Performer and the Spectator is
only 2 feet more than it was in Mr. Gar-
rick's House.

The following accurate account of the
Building of the present Drury Lane Thea-
tre will, I think, be as interesting to the
Reader as it is honourable to the Judgment
and the Integrity of Mr. Benjamin Wyatt,
the Architect who built it.

The Amount of the Original Estimate for
the present Drury Lane Theatre, as design-
ed by Mr. Benjamin Wyatt, was £118,850,
calculating on the work being completed on
the 31 st of December, 1812.

It being subsequently decided, that the
Portico and the external Composition upon
every front, excepting the West front, should
be omitted, the Estimate was reduced to the
sum of £l 1 2,750 ; those Items having stood in
the original Estimate at the sum of £6,100.

THEATRES. 189

After the Estimate had
thus been reduced to the
sum of £l 12,750, certain
extra works were decided
upon, which (previously to
such decision) were com-
puted at £11,540

During the progress of
the work it was decided
that the Theatre should
be opened to the Public
on the 10th of October,
instead of on the 31st of
December, 1812, as at first
intended ; the addition-
al expense arising from
which alteration was cal-
culated at the sum of - £1,500

Making, together with
the foregoing sum, a total

of £13.040 above the

reduced Estimate.

Which sum of £13,040
added to £112,750, (the
amount of the reduced Es-
timate) makes a total of - - - £125,790
which was the precise sum actually paid for
the Building; so that in fact the Proprietors
never were subjected to One Shilling of expense

190

THEATRES.

for the Building beyond the amount at which it
was estimated; although, from the alterations
above stated, in the work executed, the Esti-
mate was, from time to time, either diminish-
ed or augmented.

The Building was commenced on the 21st
of October, 1811, and opened to the Public
on the 10th of October, 1812, a period of
little more than eleven months.

Distance from

the Curtain to the

Front Boxes.

N umber of Per-
sons the Seats in
the Boxes will
contain.

c

V o

>>

Si

l!

o

At the JFeet.
English Opera House, K( .
in 1823. r U

700

at 5s.
175/.

650
at 3s,
97/. 10

400

at 2s.

40/.

1
Drury Lane, L n c
in 1823. j 6 °-~ 6

1134

396/. 18

700

122/. 16

500

50/.

Covent Garden, L q
in 1821. bd

1000
at 7*.
350/.

700
at 3s. 6d.
122/. 10

500

at 2s.

50/..

Haymarket,
in 1823.

750

at 5s.
187/. 10

400

at 35.

60/.

320

at 2s.
32/.

THEATRES.

191

For the foregoing Calculations I am in-
debted to Mr. Arnold, Mr. Winston, and Mr.
James Brandon.

" When His Majesty went Ho Covent Gar-
den Theatre on February 7th, 1821, the Per-
formances were Twelfth Might and Harlequin
and Friar Bacon — Twelve Hundred People
paid to the Boxes — but there is not Sitting
room for more than a Thousand." — Mr, J.

0}
09

U5

>>

CD

c

o

tn

<u
X
O

PQ

01
08

>

*S-I

250
at 1*.
12/. 10

2000

325/.

In the Private

Boxes,

160 Persons.

300
15/.

2634

534/. 14

16 Family Boxes,
124 Persons,

24 Private Boxes,
192 Persons.

300

at Is,

15/.

2500

537/.

26 Private Boxes,
172 Persons.

200

at Is.

10/.

1670

289/. 10

14 Private Boxes,
98 Persons.

■■■-

192 THEATRES.

Brandon, late Box Book-keeper to Covent
Garden Theatre.

When His Majesty visited Drury Lane
Theatre on Monday, the 1st of December,
1823, every part of it was crowded to ex-
cess — but I could not learn the exact num-
ber of the Spectators.

When The King went to Covent Garden
Theatre, on Wednesday the 3d of December,
1823, the Performances were The Cabinet
and Timour the Tartar, and the number of
Persons who paid to the

Boxes 1936

Pit 1123

Gallery 776

Upper Gallery - - - 420

4255
exclusive of Private Boxes.

The above account was given to me by
Mr. Robertson, the Treasurer to Covent Gar-
den Theatre.

It appears by this Document, that such
was the universal and earnest desire of His
Majesty's Loyal Subjects to behold their
Gracious Sovereign — that a greater number
of Persons assembled in the Theatre on that
Evening, than had ever been within it on

god! save the king. 193

any previous performance : the whole scene
was most brilliant.

" God ! save the King"

was sung several times. Many appear to
have taken much pains to shew — When our
favourite National Anthem was composed, — I
have endeavoured to shew — how it ought to
be Sung* with

" Good Emphasis and Good Discretion."

See No. 4. of " the Loyal and National Songs
of England."

Perhaps the latter information, may be as
useful as the former — for I remember to have
read in " The Cook's Oracle," that — " it is no

* Never having seen a Complete Score of " God save
THE King" for a full Band, Vocal and Instrumental, — I
have given one, and have marked the words as they ought
to be expressed, in " Thp Grand Selection of THE Loyal,
National, and Sea Songs of England, published in
Commemoration of the Coronation of King George the
Fourth, and most, humbly Insciibed, and with Giacious
Permission dedicated to the King's most Excellent
Majesty by William Kitchinpr, M.D.

Printed for Hurst, Robinson, and Co Booksellers to
His Majesty, No. 90, Ch^apside, and No. 8, Pall-
mall, in which is now first printed, from the Original
MS. in the possession of the Editor, Dr. John Bull's
" (&m BUte the KCngr"— A.D. 1616, and a Fac-
simile of the earliest printed Copy of " God save the King"
^ (1745) and 110 other Loyal, National, and Sea Songs
of England.

17

194 god! save the king.

matter how Good your Meat is,— if it is not
well Dressed."

I believe, I am entitled to the honour of
having given the first hints which have been
written, as to How what is Sung so often ought
always to be Sung.

" The Words being marked with proper Em-
phasis — it is presumed will infinitely heighten
the effect, and may be a standard for the
performance of it — and ensure, the proper
pronunciation of the Words, and the effective
expression of the Music ; and revive that har-
monious combination of them, the want of
which has long been deplored, — by all who
have faculties to comprehend how great is
their power when united, and

" Sound is married to immortal Verse." — Miltok - .

lt As soon as this is generally considered,
Singers will see their readiest road to fame,
is to avail themselves of the double power of
making the words an appeal to the Hearts
and Understandings of their Auditors—as
well as attacking their Ears with Volutas
and Cadences, &c.

"To produce effect on others — Actors
must themselves feel the passion they wish
to inspire their audience with — and to sing
with proper and effective expression, must

god! save the king. 195

give to every Syllable, and to every Quaver,
its exact relative value ; but not Shout and
Bawl upon From — To — Of — In — And — But
— On, &c. &c. merely, because they hap-
pen to be placed (improperly) under the
accented part of the Bar, or under a long
note, — or a favourite note in their voice.

" Melody is the soul of Music — Poe-
try is the soul of Melody — the warbling of
Sounds without the distinct articulation of
words pronounced with proper accent and
emphasis does not deserve to be called Sing-
ing : — it is merely playing upon the voice—
a Concerto on the Larynx, and comparatively,
as uninteresting as a Frame is without a Pic-
ture. Briefly — The Art of Singing effect-
ively — is-to Sing every word with the same
Accent and Emphasis as You would Speak it.*

* " The Pupils of our excellent English Composer Dr.
Arne, were remarkable for their proper pronunciation.—
It will be thought almost incredible when I relate that all
the fine and clear pronunciation of the words which dis-
tinguished the late Mr. Kennedy, natural as it appeared,
was the entire effect of hard up-hill application of the Doc-
tor's lofty conceptions of what was calculated to touch the
Hearts and Understanding of the Auditors. This immense
difficulty was often accompanied by tears and sobbings, as
impossibilities; but Akjve knew otherwise, and ' Omne
tulit punctum.' I say it is inconceivable what lights the
Doctor threw on the accentuation of each Word, nay on
every Letter of every word, whether commencing or finishing

196 god! save the king.

In singing " God ! save the King," if every
Syllable be sung, as it commonly is,

61 God save great George our King,"

these words are pronounced as if they were
spelt —

Gaw-od say-eev grey-eat Jaw-orge ow-er Kee-ing ;

thus making Monosyllables into Dissyllables.
w If (he proper pronunciation be preserved,
it must be thus —

God ! save great George our KirTg ;

the only syllables in this line which should
be sung, the time indicated by the notes, are—

God! save — and — George.

" This Solemn Invocation to the Almighty !
as commonly sung, sounds more like a Song
of Triumph, — than a Prayer for the preser-
vation of our Sovereign — hardly a word of
it, except the first and last line, is heard dis-
tinctly.

" How much would the effect of this Loyal
Anthem be increased, if the name of God !

with either vowels or consonants, so as to render the
of the Song intelligible to the most common ears as well as
to the most rrfiued. He would pass whole mornings, and I
never give up the Idea, that the Poetry of a Song ill ex- ■
pressed was a Nullity to the Understanding, instead of a
Blaze of Light; and thus he succeeded with the British,
Public."—- {Literary Gazette.)

god! save the king. * 197

"was uttered with due reverence ! ! ! , And if
Singers would consider, that " God save the
King," is not a florid Song, — but an Anthem, —
and like other Anthems admits of hardly any
ornament beyond an Apogiatura—

" Sing ye Praises with Understanding,"

Psalm xlvii.'ver. 7.

Instead of vying with each other, which shall
introduce most Trills — Shakes, &c. let us try
who can most distinctly articulate every
Syllable— and most effectively utter every
Word !

" The Loyal Anthem, is not a singular ex-
ample of the want of the coincidence of the
Musical, and the Prosodical Accent.

" It is almost impossible to point out a
Song, that can be sung, exactly, as it is set
down, from this want of the coincidence of
the Rhythms of the Poetry and the Music, —
which it is no easy task, even to Singers of
superior ability, to adjust perfectly—so as to
give full effect to the Poetry; and, at the same
time, preserve the Melody." — See Observa-
tions on Vocal Music and Singing.*

The following is a Specimen of the manner
of marking the Words which it is recommend-
ed to Composers to avail themselves of, as a

* Printed for Hurst and Robinson, No. 90, Cheapside,
12mo. 1821, price 4s.
17 *

198 god! save the king.

means of avoiding false Accent and Empha.*
sis of the Poetry they are s^oing to set — an«d
to Singers, to mark the Words of Songs (as
they would spe^k them) before they think about
the Tune, which will enable them to correct
any little errors of accent, which may have
inadvertently occurred in Songs already set
to music. This may almost always be ac-
complished without any detriment to the Me-
lody, and to the infinite improvement of most
Songs.

God ! save Great George, our King,
Long live oar Noble King,

God ! save the King ;
Send Him victorious,
Happy, and glorious,
Long to reign over us.

a

God ! save the King.

2.

O Lord, our God ! arise,
Scatter his enemies,

And ma lie them fall ;
Confound their politics,
Frustrate their knavish tricks,
On Thee, our hopes are fix'd,

O save us all.

god! save the king. 199

3.
Thy choicest gifts in store,
On George be pleas'd to pour,

Long may He reign ;
May He defend our Laws,
And ever give us cause,
To sing with Heart and voice,

God ! save the King.

APPENDIX :

RESPECTING SPECTACLES.

No. I.

RULES FOR CHOOSING SPECTACLES.
BY G. ADAMS, OPTICIAN.

"When the eye sensibly flattens, all delay
is dangerous ; and the longer those who feel
the want of assistance, defer the use of Spec-
tacles, the more they will increase the failure
of the eye : there are too many who pro-
crastinate the use of them, till at last they
are obliged to use glasses of 10 or 12 inches
focus, instead of those of 36 or 40, which
would otherwise have suited them ; thus pre-
ferring a real evil, to avoid one that is ima-
ginary. Mr. Thomm mentions several de-
plorable cases of this kind, particularly one
of a lady, who, through false shame, had ab-
stained from wearing Spectacles so long a
time, that at last it was impossible to suit
her, but with those adapted to eyes that have

202 APPENDIX.

been couched. Whereas the instances are
numerous of those who, by using glasses of
a long focus at the first approach of Short-
sightedness, have brought back their eyes to
their natural sight, and been able to lay aside
their spectacles for years.

These considerations point out clearly the
advantages that may be obtained by a pro-
per choice of spectacles on first wearing
them, and the importance of making such a
choice ; as the eye will endeavour to con-
form itself to any improper focus, and thus
be brought into a state of extreme age, at a
much earlier period than would have hap-
pened had they been suited with judgment.
There are very few Opticians but what must
have seen instances of those, who by habitu-
ating their eyes to too short a focus, or too
great a magnifying power, have so injured
those tender organs, as to deprive them of
future assistance from glasses. This fre-
quently happens to those who purchase their
spectacles of hawkers and pedlars, men equal-
ly ignorant of the science of optics and the
fabric of the eye.

" Let it, therefore, be carefully remember-
ed, that magnifying power is not the point
that is most to be considered in the choice
of Spectacles ; but their conformity to our

APPENDIX. 203

sight, their enabling us to see distinctly, and
with ease, at the distance we were accus-
tomed to read or work, before the use of
Spectacles became necessary : or, in other
words, glasses should so alter the disposition
of the rays, at their entrance into the eyes,
as will be most suitable to procure distinct
vision at a proper distance ; an end of the
highest import, as in this respect it places
the aged nearly on a level with the young,
and enables him to read a common print with
ease, at a period when, without assistance,
he could hardly distinguish one letter from
another,"— G. Adams on Vision, 8vo. 1789,
p. 105.

No. II.

MR. G. ADAMS' OBSERVATIONS ON
SHORT-SIGHTEDNESS.

"It is generally supposed, that the Short-
sighted become less so as they advance in
years, as the natural' shrinking and decay of
the humours of the eye lessen its convexity,
and thus adapt it better for viewing distant
objects : but among the great number of
Short-sighted that I have accommodated with*

204 APPENDIX.

glasses, I have ever found the reverse of this
theory to be true, and their eyes never re-
quired glasses less Concave, but generally
more Concave as they grow older, to enable
them to see at the same distance." — G. Adams
on Vision, 8vo. 1789, p. 126.

" I have found it necessary, in some in-
stances, to give Convex Glasses to the Short-
sighted when very far advanced in age, not
because their Eyes were grown less convex,
but to give them more light, and counteract
an extreme contraction of the pupil." — Ibid*
p. 127.

No. III.

OPTOMETERS.

Dr. Porterfield invented an Instrument
for measuring the focal distance of the Eye,
which he called an Optometer. — See Edirib.
Med. Ess. Vol. IV. p. 85.

This Optometer has been considerably im-
proved by Dr. T. Young, and has been
made by Mr. W. Cary, of the Strand, and is
easily applicable for the purpose of ascer-
taining the focal length of Spectacles re-
quired for Myopic or Presbyopic Eyes. —

APPENDIX. 205

See an Account thereof in Dr. Young's in-
teresting Lecture on the Mechanism of the
Eye in page 36 of the Phil, Trans* Vol.
XCI.

This ingenious Instrument is a valuable
succedaneum to a person residing at a dis-
tance from an Optician : — but when the
choice of Glasses can be obtained, the plain
plan I have laid down in Chapter X. is more
accurate, and more satisfactory.

No. IV.

DR. SMITH'S RULES FOR CHOOSING SPECTACLES .

" 51. In order to determine the proper-
est Glasses for defective eyes, the distance
from the eye, where an object begins to ap-
pear confused, should be found — by mea-
suring the least distance from which a Long-
sighted person can read a newspaper distinct-
ly and readily: and lwewise by measuring
the greatest and the least distances from
which a Short-sighted person can read small
print readily." — Dr. Smith's Optics, Rem. p.
8.

" Those Glasses are the properest for de-
fective Eyes, which are the least Concave, or
18

206 APPENDIX.

the least Convex of any that will answer the
purpose of distinct vision." — Ibid. p. 8.

" 58. Thus, any person may be fitted
with the properest Glasses though he lives at
a distance from the shops where they are
sold, by sending their focal distances com-
puted by the foregoing rules. But if choice
of Glasses be at hand, they may be better
fitted by trial; observing only to use those
Glasses which are the least Concave or the
least Convex of any that will fit the eye.
For since they cannot be put quite close to
the eye, the less any glass is Concave, the less
it diminishes the pictures of any objects up-
on the retina. It will also accustom the eye
to that conformation of its coats and hu-
mours, which is proper for seeing objects as
far off as it can; and consequently may pre-
vent the eye from growing more Short-sight-
ed.

" On the other hand the less any glass is
Convex, the less it magnifies the pictures of
objects upon the retina ; and also obliges the
eye to that conformation, which is requisite
for seeing the objects as near as it can. Both
which may prevent the eye in some measure
from growing more and more Long-sighted.'-
— page 9.

APPENDIX. 207

No. V.

Reasons why Elderly Persons want Spectacles
to read or work with, — By Dr. Jurin and
Dr. Smith.

Indistinctness in Old Men's Eyes, hcw
caused, and how mended by

Convex Glasses.

" 88. If the humours of the eye decay
by old age, so as by shrinking to make the
cornea and coat of the crystalline humour
grow natter than before, the light will not be
refracted enough, and for want of a sufficient
refraction will not converge to the bottom of
the eye, but to some place beyond it — and
by consequence will paint in the bottom of
the eye a confused picture ; and according
to the indistinctness of the picture, the ob-
ject will appear confused. This is the rea-
son of the decay of sight in old men, and
shews why their sight is mended by Specta-
cles. For the Convex glasses supply the de-
fect of plumpness in the eye, and by increas-
ing the refractions make the rays converge
sooner, so as to convene distinctly at the bot-

208 APPENDIX.

torn of the eye, if the glass has a due degree
of convexity.

64 89. The contrary happens in Short-
sighted men whose eyes are too plump. For
the refraction being now too great, the rays
converge and convene in these eyes before
they come to the bottom, and therefore, the
picture made in the bottom, and the vision
caused thereby, will not be distinct, unless
the object be brought so near the eye, as
that the place where the converging rays
convene may be removed to the bottom, or
that the plumpness of the eye be taken off,
and the refraction diminished by a concave
glass till it come to a due figure." — Dr.
Smith's Optics, 4to. Vol. I. pp. 27 and 28.

" Elderly persons do not see so well at
small distances as those of less age. This
happens partly from the shrinking, and part-
ly from the rigidity of the Cornea, which in-
creases with our age, and may carry out the
netrest limit of Perfect Vision from 3 or 4
inchrs. aS in children, and from about 5 or 6
inches in young adult persons, to 20, 30, 40
inches, or a greater distance ; and in this
case the eye has no assistance in viewing
near objects but only from the contraction of
the pupil, and this is not sufficient for Distinct
Vision, unless in a strong light."

APPENDIX. 209

" If the arc of the cornea shrink ^Jo^
part of an inch, this will remove the natural
distance from 15 to 77 inches: and the cornea
being now grown more rigid, the uvea will
be less able to contract it into a greater con-
vexity. While the cornea was more flexible,
the uvea was able to render it so convex as
to reduce the natural distance from 15 inches
to 5, that is to a third part : but now proba-
bly the new natural distance of 77 inches
can hardly be reduced to less than one half,
that is to 38 or 39 inches.

" Now this is probably the case of many
persons above 50 years of age, and particu-
larly my own, not to have perfect vision at a
distance less than ;>8 or 39 inches." — Dr.
Jurist's Essay on Vision, at the end of Dr.
Smith's Optics, p. 148,

No. VI.

CURIOUS EXPERIMENT.

" Into the rings of a pair of common Spec-
tacles let two pieces of Stained Glass of dif-
ferent colours be fixed ; and if these Specta-
cles should be worn in the common manner,
it is evident, that over one of the retinae will
18*

210 APPENDIX.

be diffused rays which excite some other
colour : and the consequence will be, that
neither colour will be singly perceptible, but
that some iniermethate colour will be seen.
— If the Eyes are alternately closed, so as
to exhibit the Two Colours singly, one suc-
ceeding the other, — and immediately after
both Eyes be kept open, the intermediate
colour will be very perceptible."

" If a Blue and a Yellow glass are placed
one before the other, and applied to one Eye,
the appearance will be that of a full Green ;
but if the same glasses should be applied
one before each Eye, as in the experiment
of the Spectacles or tubes, the colour will
be Green diluted with much white light, or a
pale Green ; for when the Glasses are placed
one before the other, the two in this position
intercept much more light than when they
are separate ; and this for a reason which
must be obvious to all who are acquainted
with Optics. — Dr. Crisp on Vision^ 8vo.
1796, pp. 161 and 166.

APPENDIX. 211

No. VII.

DR. WELLS ON THE CHANGES WHICH THE
VISION OF SHORT-SIGHTED PERSONS UN-
DERGOES FROM AGE.

"It has been very generally, if not uni-
versally, asserted by systematic writers up-
on Vision, that the Short-sighted are render-
ed by Age fitter for seeing distant objects
than they were in their Youth. But this
opinion appears to me unfounded in fact, and
to rest altogether upon a false analogy. If
those who possess ordinary Vision, when
young, become, from the flatness of the
cornea, or other changes in the mere struc-
ture of the eye, Long-sighted as they ap-
proach to old age, it follows, that the Short-
sighted must, from similar changes, become
better fitted to see distant objects. Such ap-
pears to have been their reasoning. But the
course pursued by nature seems very diffe-
rent from that which they have assigned to
her. For, of four Short-sighted persons of
my acquaintance, the ages of whom are be-
tween fifty-four and sixty years, and into the
state of whose vision I have inquired particu-
larly : Two have not observed that their

212 APPENDIX.

vision has changed since they were young,
and two have lately become, in respect to
distant objects, more short-sighted than they
were formerly. As the manner in which
this change has occurred is unnoticed, I be-
lieve, by any preceding author, T shall here
relate the more remarkable of the two cases.
" A gentleman became Short-sighted in
early life, and as his profession obliged him
to attend very much to minute visible objects,
he, for many years, wore spectacles with
Concave glasses almost constantly, by the
aid of which he saw as distinctly, and at as
great a variety of distances, as those who
enjoy the most perfect vision. At the age
of fifty, however, he began to observe
that distant objects, though viewed through
his glasses, appeared indistinct, and he was
hence led to fear, that his eyes were effected
with some disease. But happening one d?y
to take up, in an optician's shop, a single con-
cave glass, and to hold it before one of his
eyes, while his spectacles were on, he found,
to his great joy, that he had regained distinct
vision of distant objects. With regard to
such objects, therefore, he had lately become
shorter-sighted than he had formerly been.
But along with this change, another occur-
red of a directly opposite kind. For when

APPENDIX. 213

he wished to examine a minute object atten-
tively, such as he used to see accurately by
means of his spectacles, he now found it ne-
cessary to lay them aside, and to employ his
naked eye. He had become, therefore, in
respect to near objects, longer-sighted. The
power, consequently, in this gentleman, to
adapt the eye to different distances, is either
totally lost or much diminished ; but the
point, or small space to which his perfect vi-
sion is now confined, instead of being the
most remote to which he could formerly ac-
commodate his eyes, as is commonly the
case with the ordinarily sighted, when they
are becoming old, is now placed between the
two extremes of his former range of accurate
vision. The eyes of the other short-sighted
person, a physician of considerable learning,
whose vision has been altered by age, have
been affected in a similar manner, but not in
so great a degree.

" The only change which had occurred
from age, in the sight of such of my acquaint-
ance as were considerably myopic, was a
lessening, on both sides, of their range of
perfect vision." — From Dr. Wells, on Vision,
in the Phil. Trans. Vol. CI. p. 385.

214

APPENDIX,

No. VIII.

MR JAMES WARE THE OCULIST'S OBSERVA-
TIONS RELATIVE TO THE NEAR AND DIS-
TANT SIGHT OF DIFFERENT PERSONS.
From the 103d Vol. of Phil. Trans, p. 31.

"The fact that Near-s'ghtedness most com-
monly commences at an early period of life,
and Distant-sightedness generally at an ad-
vanced age, is universally admitted. Near-
sightedness generally comes* on between the
ages of ten and eighteen. The discovery of
it most commonly arises from accident ; and,
at first, the inconvenience it occasions is so
little, that it is not improbable the imperfec-
tion would remain altogether unnoticed, if a
comparison were not instituted with the sight
of others, or if the experiment were not made
of looking through a Concave glass."

" It should be remembered, that for com-
mon purposes every Near-sighted Eye can
see with nearly equal accuracy through two
glasses, one of which is one number deeper
than the other ; and though the Sight be in
a high degree more assisted by the deepest

* It is generally observed as soon as persons begin to
use their Eyes in earnest.— W. K.— '

APPENDIX. 215

of these than by the other, yet, on its being
first used, the deepest number always occa-
sions an uneasy sensation, as if the Eye was
strained. If, therefore, the glass that is most
concave be at first employed, the Eye, in a
little time, will be accommodated to it, and
then a glass one number deeper may be used
with similar advantage to the Sight ; and if
the wish for enjoying the most perfect vision
be indulged, this glass may soon be changed
for one that is a number still deeper, and so
in succession, until, at length, it will be diffi-
cult to obtain a glass sufficiently concave to
afford the assistance that the Eye requires.*
p. 34.

" Although old persons lose the power of
distinguishing correctly near objects, and re-
quire for this purpose the aid of convex
glasses, they usually retain the sight of those
that are distant, as well as when they were
young. Instances, however, are not want-

* I have observed, that most of the Near-sighted per-
sons with whom I have had an opportunity of conversing,
have had the right eye more near-sighted than the left ;
and I think it not improbable, that this difference between
the two eyes has been occasioned by the habit of using a
single concave hand-glass ; which, being most commonly
applied to the right eye, contributes, agreeably to the re-
mark above-mentioned, to render this eye more near-sight-
ed than the other.

216 APPENDIX.

ing, of persons advanced in life, who require
the aid of convex glasses to enable them to
see near, as well as distant objects, p. 43.

" My own case," Mr. Ware observes,
"militates against the common observation,
that, as Near-sighted pprsons grow older they
become less Near-sighted ; since my Eyes,
on the contrary, are more Near-sighted, at
the age of fifty-five, than they were at twen-
ty-five, and I am now obliged to employ
deeper concave glasses than I then used to
see distant objects, though I am not able to
see distinctly through them things that are
near.

" The alteration which has taken place in
my range of vision, 1 have reason to believe,
is not unusual. — The following is an instance
of this kind, that is still more remarkable.
Mr. L., sixty-six years of age, who has spent
a great part of his life in the West Indies,
and whose sight, when he was young, ena-
bled him to see both Near and Distant ob-
jects with great precision, began, at the age
of forty, to experience a difficulty in reading
and writing. He immediately procured con?
vex Spectacles of the first number sold by
Opticians, which glasses are usually ground
to a focus of forty-six* or forty-eight inches.

^ * Read thirty-six.— W. K,

APPENDIX. 217

and by the aid of these he continued to read
and write with ease (distinguishing perfectly
in the usual way all distant objects without
them,) until he was fifty. At this time he
first began to perceive an indistinctness in
the appearance of things at a distance ; and,
on trying with different glasses, he discover-
ed that, by looking through a double-concave
glass of the sixth number, (which is ground
to a radius of eight inches on one side and
eleven inches on the other,) he was enabled to
see distant objects distinctly. He has continu-
ed to use glasses of this description, for the
purpose of seeing distant objects, from that
time to the present; but is obliged to remove
them whenever he reads, and still to employ
the first number of a convex glass. — In this
instance a presbyopic was changed to a myo-
pic sight, without any known efficient cir-
cumstance to produce it. p. 47.

" In addition to these cases, I beg leave to
add the information I have received from an
eminent Mathematical Instrument-maker,
about fifty years of age, who has long made
use of convex glasses to assist his sight in
reading. He tells me, that when he has been
employed many hours together, for several
successive, days, in looking through a double
microscope that magnifies twenty-eight times,
19

218 APPENDIX.

(in order to enable him to mark the degrees
on a small brass plate,) he has afterwards
been able, repeatedly, for a few weeks, to
read without his glasses ; but then the amend-
ment gradually ceases, and he is soon oblig-
ed to return to the use of the same glasses
that he had worn before."

No. IX.

AN APPENDIX TO MR. WARE'S PAPER ON VISION.

BY SIR CHARLES BLAGDEN, F.R.S.

In Vol. 103 of Phil. Trans, p. 110.

" Mr. Ware states in his Paper, that Near-
sightedness comes on most frequently at an
early age 5 that it is more common in the
higher than the lower ranks of life ; and that
particularly at the Universities, and various
colleges, a large proportion of the students
make use of concave glasses. All this is ex-
actly true, and to be accounted for by one
single circumstance, namely, the habit of
looking at near objects. Children born with
eyes which are capable of adjusting them-
selves to the most distant objects, gradually
lose that power soon after they begin to read
and write ; those who are most addicted to

APPENDIX. 219

study become Near-sighted more rapidly; «
and, if no means are used to counteract the
habit, their eyes at length lose irrecoverably
the faculty of being brought to the adjust-
ment for parallel rays. Of this I am myself
an example, and as I recollect distinctly the
progress, it may not be useless to record it
here.

" When I first learnt to read, at the usual
age of four or five years, I could see most
distinctly, across a wide church, the contents
of a table, on which the Lord's Prayer and
the Belief were painted in suitably large let-
ters. In a few years, that is about the ninth
or tenth of my age, being much addicted to
books, I could no longer read what was paint-
ed on this table : but the degree of Near-
sightedness was then so small, that 1 found a
watch-glass, though as a meniscus it made
the rays diverge very little, sufficient to en- -
able me to read the table as before. In a
year or two more, the watch-glass would no
longer serve my purpose ; but being dissuad-
ed from the use of a common concave glass,
as likely to injure my sight, I suffered the
inconvenience of a small degree of myopy,
till I was more than thirty years of age.
That inconvenience, however, gradually
though slowly increasing all the time, at

220 APPENDIX.

length became so grievous, that at two or
three-and-thirty, I determined to try a con-
cave glass: and then found that the numbers
2 and 3 were to me in the relation so well
described by Mr. Ware ; that is, I could see
distant objects tolerably well with the former
number, but still more accurately with the
latter. After contenting myself a little time
with No. 2, I laid it wholly aside for No. 3,
and, in the course of a few more years, came
to No. 5, at which point my eye has now
been stationary between fifteen and twenty
years. An earlier use of concave glasses
would probably have made me more Near-
sighted, or would have brought on my pre-
sent degree of myopy at an earlier period of
life. If my friends had persuaded me to
read and write with the book or paper al-
ways as far from my eye as I could see ; or
if I had occasionally intermitted study, and
taken to field sports, or any employment
which would have obliged me to look much
at distant objects, it is very probable that I
might not have been Near-sighted at all.
Possibly the persons who become Near-sight-
ed, by having constantly to adjust their eyes "
to near objects, may not usually change to
be Long-sighted by "Age," p. 111.

APPENDIX, 221

No. X.

FROM DR. HERSCHEL'S PAPER ON THE POWER
OF PENETRATING INTO SPACE BY TELE-
SCOPES.

[In Vol. XC. of the Phil. Trans, p. 49/|

" The Aperture of the Pupil of the Eye
in different persons differs considerably. Its
changes are not easily to be ascertained ;
but we shall not be much out in stating its
variations to be chiefly between 1 and 2
tenths of an inch. Perhaps this may be sup-
posed under-rated, for the powers of vision
in a room completely darkened will exert
themselves in a very extraordinary manner.
In some experiments on light, made at Bath,
in the year 1 780, T have often remarked that,
after staying some time in a room fitted up
for these experiments, where, on entering, I
could not perceive any one object, I was no
longer at a loss, in half an hour's time, to find
every thing I wanted. It is, however, pro-
bable that the opening of the Iris is not the
only cause of seeing better after remaining
long in the dark, but that the tranquillity of
the retina, which is not disturbed by foreign
objects of vision, may render it fit to receive
impressions such as otherwise would have

222 - APPENDIX.

been too faint to be perceived. This seems
to be supported by telescopic vision, for it
has often happened to me in a fine winter's
evening, when at midnight, and in the ab-
sence of the Moon, I have taken sweeps of
the Heavens, of four, five, or six hours' du-
ration, that the sensibility of the Eye, incon-
sequence of the exclusion of light from sur-
rounding objects, by means of a Black Hood
which I wear upon those occasions, has been
very great ; and it is evident that the open-
ing of the Iris would have been of no service
in these cases, on account of the diameter of
the optic pencil, which, in the 20 feet tele-
scope, at the time of sweeping, was no more
than the 12th of an inch.

" The effect of this increased sensibility
was such, that if a star of the 3d magnitude
came towards the field of view, I found it
necessary to withdraw the eye before its en-
trance, in order not to injure the delicacy of
vision, acquired by long continuance in the
dark. The transit of large stars, unless
where none of the 6th or 7th magnitude could
be had, have generally been declined in my
sweeps, pven wi s h the 20 feet Telescope.'
And I remember, that after a considerable
sweep with the 40 feet instrument, the ap-
pearance of Qirius announced itself at a great

APPENDIX. 223

distance, like the dawn of morning, and came
on by degrees, increasing in brightness, till
this brilliant star at last entered the field of
the telescope, with all the splendour of the
rising Sun, and forced me to take the eye
from that beautiful sight. Such striking ef-
fects are a sufficient proof of the great sensi-
bility of the Eye acquired by keeping it from
the Light, p. 54.

"On taking notice, in the beginning of
sweeps, of the times that passed, I found that
the eye, coming from the light, required near
20 seconds before it would be sufficiently re-
posed to admit a view of very delicate ob-
jects in the telescope ; and that the observa-
tion of a transit of a star of the 2d or 3d
magnitude would disorder the eye again, so
as to require the same time for the re-estab-
lishment of its tranquillity.

"The difficulty of ascertaining the greatest
opening of the Eye arises from the impossibi-
lity of measuring it at the time of its extreme
dilatation, which can only happen when eve-
ry thing is completely dark."

£24 APPENDIX*

No. XI.

SNOW SPECTACLES.

These appear as if formed of half the Mar-
row-bone of a Leg of Mutton* and are worn
by our untutored fellow creatures, to guard
their Eyes from the glare of light from the
Snow. See page 82.

The following are the dimensions of a pair
which were lent to me, and correspond very
nearly with those mentioned at page 99.

Length of Front 4 T 6 g-ths.

Breadth across it lf^ths.

Distance between the Eye slits l^ths.

The Eye slits in length l T 3 ^ths.

Ditto in breadth T Lth.

The part which answers to the knuckle
t%ths.

They are fixed on the head by skin Straps
about an Inch broad, which also serve to
defend the Eyes from side light.

THE END*

[Oct., 1884, 20,000]

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